Secret Worlds: The Universe Within - Soar through space starting at 10 million light years away from the Milky Way down through to a single proton in Florida in decreasing orders of magnitude (powers of ten). This tutorial explores the use of exponential notation to understand and compare the size of things in our world and the universe, and provides a glimpse of the duality between the macroworld around us and the hidden microworld within.

Electromagnetic Radiation - Visible light is a complex phenomenon that is classically explained with a simple model based on propagating rays and wavefronts, a concept first proposed in the late 1600s by Dutch physicist Christiaan Huygens. Electromagnetic radiation, the larger family of wave-like phenomena to which visible light belongs (also known as radiant energy), is the primary vehicle transporting energy through the vast reaches of the universe. The mechanisms by which visible light is emitted or absorbed by substances, and how it predictably reacts under varying conditions as it travels through space and the atmosphere, form the basis of the existence of color in our universe

Spinning Disk Confocal Microscopy - Spinning disk microscopy has advanced significantly in the past decade and now represents one of the optimum solutions for both routine and high-performance live-cell imaging applications. The rapid expansion in biomedical research using live-cell imaging techniques over the past several years has been fueled by a combination of events that include dramatic advances in spinning disk confocal microscopy instrumentation coupled with the introduction of novel ultra-sensitive detectors and continued improvements in the performance of genetically-encoded fluorescent proteins.

Spectral Imaging and Linear Unmixing - Spectral imaging and linear unmixing is becoming an important staple in the microscopist's toolbox, particularly when applied to the elimination of autofluorescence and for FRET investigations. Instruments equipped for spectral imaging are becoming increasingly popular and many confocal microscopes now offer this capability. Widefield fluorescence and brightfield microscopy are also being used more frequently for resolving complex fluorophore and absorbing dye mixtures, a trend that should continue into the future.

Fluorescent Protein Technology - It took over thirty years, and the advent of recombinant DNA as well as vastly improved molecular biological approaches to see the pioneering work of Osamu Shimomura developed into a useful tool for live-cell imaging by Doug Prasher and Martin Chalfie. Just in the past decade, however, we have witnessed a truly remarkable expansion in the fluorescent protein palette, largely driven by the innovative studies from Roger Tsien's laboratory. Most of the fluorescent proteins that are commonly used today have been modified through mutagenesis to optimize their expression in biological systems. Continued efforts using directed evolution approaches will no doubt improve the spectral characteristics, photostability, maturation time, brightness, acid resistance, and utility of the fluorescent protein tags for cellular imaging.

Carl Zeiss MicroImaging Online Campus - Visit the new ZEISS website that explores the fascinating world of optical microscopy and provides the necessary background to understand both the basic concepts and advanced principles. Included are review articles, interactive Flash tutorials, reference materials, and image galleries.

Light Sources for Optical Microscopy - The performance of the various illumination sources available for optical microscopy depends on the emission characteristics and geometry of the source, as well as the focal length, magnification and numerical aperture of the collector lens system. In gauging the suitability of a particular light source, the important parameters are structure (the spatial distribution of light, source geometry, coherence, and alignment), the wavelength distribution, spatial and temporal stability, brightness, and to what degree these various parameters can be controlled.

Mag Lab U: Learning about Electricity and Magnetism - Visit our sister website for interactive Java tutorials, a timeline of historical events, a museum of antique devices, and articles on topics related to electricity and magnetism.

Live-Cell Imaging - An increasing number of investigations are using live-cell imaging techniques to provide critical insight into the fundamental nature of cellular and tissue function, especially due to the rapid advances that are currently being witnessed in fluorescent protein and synthetic fluorophore technology. As such, live-cell imaging has become a requisite analytical tool in most cell biology laboratories, as well as a routine methodology that is practiced in the wide ranging fields of neurobiology, developmental biology, pharmacology, and many of the other related biomedical research disciplines. Among the most significant technical challenges for performing successful live-cell imaging experiments is to maintain the cells in a healthy state and functioning normally on the microscope stage while being illuminated in the presence of synthetic fluorophores and/or fluorescent proteins.

Comparing Confocal and Widefield Fluorescence Microscopy - Confocal microscopy offers several distinct advantages over traditional widefield fluorescence microscopy, including the ability to control depth of field, elimination or reduction of background information away from the focal plane (that leads to image degradation), and the capability to collect serial optical sections from thick specimens. The basic key to the confocal approach is the use of spatial filtering techniques to eliminate out-of-focus light or glare in specimens whose thickness exceeds the dimensions of the focal plane. This interactive tutorial explores and compares the differences between specimens when viewed in a confocal versus a widefield fluorescence microscope.

Fluorescence (Förster) Resonance Energy Transfer with Fluorescent Proteins - Fluorescent proteins are increasingly being applied as non-invasive probes in living cells due to their ability to be genetically fused to proteins of interest for investigations of localization, transport, and dynamics. In addition, the spectral properties of fluorescent proteins are ideal for measuring the potential for intracellular molecular interactions using the technique of Förster (or fluorescence) resonance energy transfer (FRET) microscopy. Because energy transfer is limited to distances of less than 10 nanometers, the detection of FRET provides valuable information about the spatial relationships of fusion proteins on a sub-resolution scale. This interactive tutorial explores various combinations of fluorescent proteins as potential FRET partners and provides information about critical resonance energy transfer parameters, as well as suggestions for microscope optical filter and light source configuration.

The Fluorescent Protein Color Palette - A broad range of fluorescent protein genetic variants have been developed over the past several years that feature fluorescence emission spectral profiles spanning almost the entire visible light spectrum. Extensive mutagenesis efforts in the original jellyfish protein have resulted in new fluorescent probes that range in color from blue to yellow and are some of the most widely used in vivo reporter molecules in biological research. Longer wavelength fluorescent proteins, emitting in the orange and red spectral regions, have been developed from the marine anemone Discosoma striata and reef corals belonging to the class Anthozoa. Still other species have been mined to produce similar proteins having cyan, green, yellow, orange, red, and far-red fluorescence emission. Developmental research efforts are ongoing to improve the brightness and stability of fluorescent proteins, thus improving their overall usefulness.

Introduction to Image Processing and Analysis - John Russ has taught hands-on courses and extended workshops in image processing and analysis to more than 3000 students, worldwide, over the course of his career. His one-day tutorials and lectures, sponsored by various professional societies and other organizations, have reached several thousand more. But the need to have a basic understanding of these topics is far wider than he can ever reach in person. Potentially everyone working with images, and certainly that includes every microscopist, needs to be aware of the possibilities (and limitations) of computer-based image processing and measurement. The descriptive reviews and interactive tutorials in this section cover most of the topics that the author discusses in typical one-day tutorials.

Fluorescent Protein Fluorophore Maturation Mechanisms - Autocatalytic formation of the fluorophore (also referred to as a chromophore) within the shielded environment of the polypeptide backbone during fluorescent protein maturation follows a surprisingly unified mechanism, especially considering the diverse natural origins of these useful biological probes. Shortly after synthesis, most fluorescent proteins slowly mature through a multi-step process that consists of folding, initial fluorophore ring cyclization, and subsequent modifications of the fluorophore. The spectral properties of fluorescent proteins are dependent upon the structure of the fluorophore as well as the localized interactions of amino acid residues in the immediate vicinity, and in some cases, residues far removed from the fluorophore. The interactive tutorials in this section explore fluorophore formation in a wide variety of spectrally diverse fluorescent proteins deduced from crystallographic studies.

The Virtual Rat - The humble rat has had an outsized impact on human history. In the Middle Ages, the black rat (Rattus rattus) was blamed for spreading the Black Plague through its fleas, a pandemic that killed a third of Europe's population, an estimated 34 million people. In modern times, however, a larger cousin, the Brown rat (Rattus norvegicus) has become an important model organism in biological research. Selective breeding of the Brown Rat has produced the albino laboratory rat. Rats grow quickly to sexual maturity and are easy to keep and breed in captivity. Scientists have bred many strains or "lines" of rats specifically for experimentation. Generally, these lines are not transgenic because the easy techniques of genetic transformation that work in mice do not work as well for rats. This has been a problem for investigators who view rat behavior and physiology as more relevant to humans and easier to observe than in mice. In October 2003, researchers succeeded in cloning two laboratory rats by the problematic technique of nuclear transfer. As cloning techniques are perfected, rats likely will become an important subject of genetic research.

Rat Brain Tissue Sections - The rat brain has served as an excellent model for elucidating the complex anatomy and physiological mechanisms of the human brain. As a result, a significant amount of information on brain diseases, such as dementia and Parkinson's disease, has been determined from investigations using rat brains. Brain tissue has been mapped into dozens of major and hundreds of minor regions that are anatomically and functionally distinct. Individual brain cells segregate into specialized areas by expressing a wide spectrum of specific housekeeping proteins, enzymes, transporters, and receptors. This digital image gallery explores many regions of the rat brain as observed with immunofluorescence in coronal, horizontal, and sagittal thick sections using laser scanning confocal microscopy.

Cells in Motion - In multicellular tissues, such as those found in animals and humans, individual cells employ a variety of locomotion mechanisms to maneuver through spaces in the extracellular matrix and over the surfaces of other cells. Examples are the rapid movement of cells in developing embryos, organ-to-organ spreading of malignant cancer cells, and the migration of neural axons to synaptic targets. Unlike single-celled swimming organisms, crawling cells in culture do not possess cilia or flagella, but tend to move by coordinated projection of the cytoplasm in repeating cycles of extension and retraction that deform the entire cell. The digital videos presented in this gallery investigate animal cell motility patterns in a wide variety of morphologically different specimens. Requires the RealPlayer browser plug-in.

Laser Scanning Confocal Microscope Simulator - Perhaps the most significant advance in optical microscopy during the past decade has been the refinement of mainstream laser scanning confocal microscope (LSCM) techniques using improved synthetic fluorescent probes and genetically engineered proteins, a wider spectrum of laser light sources coupled to highly accurate acousto-optic tunable filter control, and the combination of more advanced software packages with modern high-performance computers. This interactive tutorial explores multi-laser fluorescence and differential interference contrast (DIC) confocal imaging using the Olympus FluoView FV1000 confocal microscope software interface as a model.

Nikon MicroscopyU - The MicroscopyU website is designed to provide an educational forum for all aspects of optical microscopy, digital imaging, and photomicrography. Together with the scientists and programmers at Molecular Expressions, Nikon microscopists and engineers are providing the latest state-of-the-art information in microscope optics and imaging technology including specialized techniques such as fluorescence, differential interference contrast (DIC), phase contrast, reflected light microscopy, and microscopy of living cells. We invite you to explore MicroscopyU and discover more about the exciting world of optics and microscopy.

Olympus Image of the Year Award - Inspired by the beauty and breadth of images submitted for the 2018 Image of the Year Award held in Europe, Olympus is continuing to search for the best light microscopy images in 2019—this time on a global scale. Olympus’ first Image of the Year Global Life Science Light Microscopy Award recognizes the very best in life science imaging worldwide.

Fluorescence Microscopy of Cells in Culture - Serious attempts at the culture of whole tissues and isolated cells were first undertaken in the early 1900s as a technique for investigating the behavior of animal cells in an isolated and highly controlled environment. The term tissue culture arose because most of the early cells were derived from primary tissue explants, a technique that dominated the field for over 50 years. As established cell lines emerged, the application of well-defined normal and transformed cells in biomedical investigations has become an important staple in the development of cellular and molecular biology. This fluorescence image gallery explores over 30 of the most common cell lines, labeled with a variety of fluorophores using both traditional staining methods as well as immunofluorescence techniques.

Human Pathology Digital Image Gallery - The investigation of disease in humans has, understandably, been one of the primary focal points in medicine for thousands of years. The image gallery presented in this section attempts to illustrate, through use of the brightfield microscope, many of the pathological conditions that are readily observed in stained human specimens. Each image was chosen for artistic merit, photographic quality, and content. Note that several of the images in this gallery might not depict every aspect of the pathological condition under which they are catalogued.

Nikon Fluorescence Microscopy Digital Image Gallery - The widefield reflected light fluorescence microscope has been a fundamental tool for the examination of fluorescently labeled cells and tissues since the introduction of the dichromatic mirror in the late 1940s. Furthermore, advances in synthetic fluorophore design coupled to the vast array of commercially available primary and secondary antibodies have provided the biologist with a powerful arsenal in which to probe the minute structural details of living organisms with this technique. In the late twentieth century, the discovery and directed mutagenesis of fluorescent proteins added to the cadre of tools and created an avenue for scientists to probe the dynamics of living cells in culture. This gallery examines the fluorescence microscopy of both cells and tissues with a wide spectrum of fluorescent probes.

Burgers 'n Fries - Join us for a microscopic examination of America's culinary favorite: the ubiquitous hamburger and French fries. Discover how this delightful classic is just as beautiful as it is tasty.

Chemical Crystals - Chemical compounds can exist in three basic phases, gaseous, liquid, or solid. Gases consist of weakly bonded atoms and expand to fill any available space. Solids are characterized by strong atomic bonding and have a rigid shape. Most are crystalline, having a three-dimensional periodic atomic arrangement. Some, such as glass, lack this periodic arrangement and are noncrystalline, or amorphous. Liquids have characteristics that fall in between gases and solids. This cinemicrographic collection presents time-lapse movies of various chemical compounds as they change physical states.

Scanning Electron Microscopy - We have teamed up with award-winning electron microscopist Dennis Kunkel to produce a virtual Scanning Electron Microscope (vSEM). Visitors can adjust the focus, contrast, and magnification of microscopic creatures viewed at thousands of times their actual size.

Laser Scanning Confocal Microscopy - (approximately a 30 second download on 28.8K modems) Several methods have been developed to overcome the poor contrast inherent with imaging thick specimens in a conventional microscope. Specimens having a moderate degree of thickness (5 to 15 microns) will produce dramatically improved images with either confocal or deconvolution techniques. The thickest specimens (20 microns and above) will suffer from a tremendous amount of extraneous light in out-of-focus regions, and are probably best-imaged using confocal techniques. This tutorial explores imaging specimens through serial z-axis optical sections utilizing a virtual confocal microscope.

Stereoscopic Zoom Microscopy - Many stereoscopic microscopes feature the ability to perform a continuous magnification change by means of a zoom lens system placed between the objective and the eyepieces. Explore zoom magnification, focus, and illumination intensity in stereoscopic microscopes with this interactive Flash tutorial.

Java-powered QX3 Computer Web Microscope - This virtual QX3 microscope is broadcasting images over the Web at 20 frames/second, which can be viewed in a specially designed Java client run through your Web browser at frame rates up to 18 frames/second. No additional software is needed, but don't try this unless you have a fast connection (10 Mbits/sec Ethernet or higher). With this software, you can capture single digital images, record movies, and perform time-lapse cinematography experiments.

Museum of Microscopy - Featuring 3-D Studio Max drawings of ancient microscopes, this unique gallery explores many of the historic microscopes made during the last four centuries. Visit the gallery and download a copy of our Windows screen saver containing selected images of these beautiful microscopes.

Silicon Zoo - This popular gallery features images of cartoon characters and other doodling placed onto computer chips by their designers.

Featured Microscopist - Our featured microscopist for Spring 2002 is noted Dutch photomicrographer Loes Modderman. Born in Amsterdam in 1944, Modderman received her first microscope by age 13 and has never lost her sense of wonder at the minute beauties available with this instrument. Many years ago, Loes initiated a series of chemical crystallization experiments, which allowed her to meld longtime interests in nature, art, science, and photography to form her abstract photomicrographs into a colorful celebration of form and structure. A wide spectrum of these photomicrographs are featured in this gallery.

Cell and Virus Structure - Although the human body contains over 75 trillion cells, the majority of life forms exist as single cells that perform all the functions necessary for independent existence. Most cells are far too small to be seen with the naked eye and require the use of high-power optical and electron microscopes for careful examination.

Fluorescence Microscopy Digital Image Gallery - Featuring specimens collected from a wide spectrum of disciplines, the fluorescence gallery contains a variety of examples using both specific fluorochrome stains and autofluorescence. Images were captured utilizing either a Nikon DXM 1200 digital camera, an Optronics MagnaFire Peltier-cooled camera, or classical photomicrography on film with Fujichrome Provia 35 millimeter transparency film.

Pond Life - Freshwater ponds provide a home for a wide variety of aquatic and semi-aquatic plants, insects, and animals. The vast majority of pond inhabitants, however, are invisible until viewed under the microscope. Beneath the placid surface of any pond is a microscopic metropolis bustling with activity as tiny bizarre organisms pursue their lives; locomoting, eating, trying not to be eaten, excreting, and reproducing. In this collection of digital movies, observe the activities of microscopic organisms taken from a typical North Florida pond.

Concepts in Digital Imaging Technology - Explore the basic concepts in digital imaging with our illustrated discussions and interactive tutorials. Topics covered include CCD operation, image capture, digital manipulation of images and a wide spectrum of other issues in this emerging field.

Science, Optics & You - Explore our science curriculum package being developed for teachers, students, and parents. Activities are designed to promote the asking and answering of questions related to light, color, and optics. The program begins with basic information about lenses, shadows, prisms, and color, leading up to the use of sophisticated instruments scientists use to help them understand the world.

Intel Play QX3 Computer Microscope - Take a moment to visit our in-depth discussion of this incredible toy microscope. Included topics are the QX3 hardware (microscope), interactive microscope software, suggested specialized techniques, and digital image galleries from the QX3 microscope.

Creative Photomicrography - By employing multiple exposure photomicrography, we have succeeded in generating a series of unusual micrographs which we have termed microscapes. These micrographs are intended to resemble surrealistic/alien landscapes.

Digital Image Processing Interactive Java Tutorials - Explore the basic concepts of digital image processing applied to specimens captured in the microscope. Techniques reviewed include contrast, color balance, spatial resolution, image sampling frequency, geometric transformation, averaging, measurements, histogram manipulation, convolution kernels, filtering digital images, compression, noise reduction, and binary digital images.

Full-Frame CCD Operation - Having the simplest architecture and being the easiest devices to build and operate, full-frame charged coupled devices (CCDs) feature high-density pixel arrays capable of producing digital images with the highest resolution currently available. Explore how images are captured and transferred to serial output registers with this interactive Java tutorial.

Intel Play QX3 Computer Microscope Simulator - Discover how the hardware and software of this amazing "toy" microscope work together to produce images that you can digitally manipulate with a personal computer.

Geometrical Construction of Ray Diagrams - A popular method of representing a train of propagating light waves involves the application of geometrical optics to determine the size and location of images formed by a lens or multi-lens system. This tutorial explores how two representative light rays can establish the parameters of an imaging scenario.

Reflected Light Confocal Microscopy - Explore microscopy of integrated circuits using real-time confocal observations at a resolution of 0.18 microns with this interactive Java tutorial.

Building A Charged Coupled Device - Explore the steps utilized in the construction of a charged coupled device (CCD) as a portion of an individual pixel gate is fabricated on a silicon wafer simultaneously with thousands or even millions of neighboring elements.

Astigmatism - Astigmatism aberrations are similar to comatic aberrations, however these artifacts are not as sensitive to aperture size and depend more strongly on the oblique angle of the light beam. The aberration is manifested by the off-axis image of a specimen point appearing as a line or ellipse instead of a point.

Video Signal Generation - A video signal is a recoverable train of electrical impulses generated by scanning a two-dimensional image produced by the optical train of a microscope. The image is sequentially scanned in narrow strips and combined to produce the final signal. This interactive tutorial explores the relationship between the microscope image, scan lines, and the video signal.

Airy Pattern Formation - When an image is formed in the focused image plane of an optical microscope, every point in the specimen is represented by an Airy diffraction pattern having a finite spread. This occurs because light waves emitted from a point source are not focused into an infinitely small point by the objective, but converge together and interfere near the intermediate image plane to produce a three-dimensional Fraunhofer diffraction pattern.

Fluorescence Microscope Light Pathways - This interactive tutorial explores illumination pathways in the Olympus BX51 research-level upright microscope. The microscope drawing presented in the tutorial illustrates a cut-away diagram of the Olympus BX51 microscope equipped with a vertical illuminator and lamphouses for both diascopic (tungsten-halogen) and epi-fluorescence (mercury arc) light sources. Sliders control illumination intensity and enable the visitor to select from a library of five fluorescence interference filter combinations that have excitation values ranging from the near ultraviolet to long-wavelength visible light.

Condenser Alignment - This tutorial demonstrates how the condenser is centered in the optical path and the size of the field diaphragm opening is determined when adjusting a microscope for proper Köhler illumination.

If you need information about optical microscopy, how to set up a microscope, or how to take photographs with a microscope, then visit our Microscopy Primer for a detailed discussion.

Basic Concepts in Digital Image Processing - Digital image processing enables the reversible, virtually noise-free modification of an image in the form of a matrix of integers instead of the classical darkroom manipulations or filtration of time-dependent voltages necessary for analog images and video signals. Even though many image processing algorithms are extremely powerful, the average user often applies operations to digital images without concern for the underlying principles behind these manipulations. The images that result from careless manipulation are often severely degraded or otherwise compromised with respect to those that could be produced if the power and versatility of the digital processing software were correctly utilized.

Introduction to CMOS Image Sensors - CMOS image sensors are designed with the ability to integrate a number of processing and control functions, which lie beyond the primary task of photon collection, directly onto the sensor integrated circuit. These features generally include timing logic, exposure control, analog-to-digital conversion, shuttering, white balance, gain adjustment, and initial image processing algorithms. Inexpensive CMOS image sensors are entering the field of optical microscopy in educational instruments that combine acceptable optical quality with user-friendly control and imaging software packages.

Introduction to Prisms and Beamsplitters - Prisms and beamsplitters are essential components that bend, split, reflect, and fold light through the pathways of both simple and sophisticated optical systems. Cut and ground to specific tolerances and exact angles, prisms are polished blocks of glass or other transparent materials that can be employed to deflect or deviate a light beam, rotate or invert an image, separate polarization states, or disperse light into its component wavelengths. Many prism designs can perform more than one function, which often includes changing the line of sight and simultaneously shortening the optical path, thus reducing the size of optical instruments.

Stereomicroscopy - Stereomicroscopes have characteristics that are valuable in situations where three-dimensional observation and perception of depth and contrast is critical to the interpretation of specimen structure. These instruments are also essential when micromanipulation of the specimen is required in a large and comfortable working space. The wide field of view and variable magnification displayed by stereomicroscopes is also useful for construction of miniature industrial assemblies, or for biological research that requires careful manipulation of delicate and sensitive living organisms.

Basic Microscope Ergonomics - In order to view specimens and record data, microscope operators must assume an unusual but exacting position, with little possibility to move the head or the body. They are often forced to assume an awkward work posture such as the head bent over the eye tubes, the upper part of the body bent forward, the hand reaching high up for a focusing control, or with the wrists bent in an unnatural position.

Image Formation - In the optical microscope, image formation occurs at the intermediate image plane through interference between direct light that has passed through the specimen unaltered and light diffracted by minute features present in the specimen. The image produced by an objective lens is conjugate with the specimen, meaning that each image point at the intermediate plane is geometrically related to a corresponding point in the specimen.

Basic Properties of Digital Images - Continuous-tone images are produced by analog optical and electronic devices, which accurately record image data by several methods, such as a sequence of electrical signal fluctuations or changes in the chemical nature of a film emulsion that vary continuously over all dimensions of the image. In order for a continuous-tone or analog image to be processed or displayed by a computer, it must first be converted into a computer-readable form or digital format. This process applies to all images, regardless the origin and complexity, and whether they exist as black and white (grayscale) or full color. A digital image is composed of a rectangular (or square) pixel array representing a series of intensity values and ordered through an organized (x,y) coordinate system.

Introduction to Confocal Microscopy - Confocal microscopy offers several advantages over conventional optical microscopy, including controllable depth of field, the elimination of image degrading out-of-focus information, and the ability to collect serial optical sections from thick specimens. The key to the confocal approach is the use of spatial filtering to eliminate out-of-focus light or flare in specimens that are thicker than the plane of focus. There has been a tremendous explosion in the popularity of confocal microscopy in recent years, due in part to the relative ease with which extremely high-quality images can be obtained from specimens prepared for conventional optical microscopy, and in its great number of applications in many areas of current research interest.

Electronic Imaging Detectors - The range of light detection methods and the wide variety of imaging devices currently available to the microscopist make the selection process difficult and often confusing. This discussion is intended to aid in understanding the basics of light detection and to provide a guide for selecting a suitable detector for specific applications in optical microscopy.

Troubleshooting Classical and Digital Photomicrography - Photography through the microscope is undergoing a transition from film to digital imaging. New digital technologies are producing higher resolution micrographs, but the quality still falls short of that obtainable with film. Microscope configuration errors represent the greatest obstacle to quality photomicrographs, followed by errors in filter selection, film choice, aberration, dirt and debris, and processing mistakes.

Oblique or Anaxial Illumination - Achieving conditions necessary for oblique illumination, which has been employed to enhance specimen visibility since the dawn of microscopy, can be accomplished by a variety of techniques with a simple transmitted optical microscope. Perhaps the easiest methods are to offset a partially closed condenser iris diaphragm or the image of the light source. In former years, some microscopes were equipped with a condenser having a decenterable aperture iris diaphragm. The device was engineered to allow the entire iris to move off-center in a horizontal plane so that closing the circular diaphragm opening would result in moving the zeroth order to the periphery of the objective rear focal plane. In advanced models, the entire diaphragm was rotatable around the axis of the microscope so that oblique light could be directed toward the specimen from any azimuth to achieve the best desired effect for a given specimen.

Multiphoton Excitation Microscopy - Multiphoton fluorescence microscopy is a powerful research tool that combines the advanced optical techniques of laser scanning microscopy with long wavelength multiphoton fluorescence excitation to capture high-resolution, three-dimensional images of specimens tagged with highly specific fluorophores.

Flying Osprey - A Hewlett-Packard design team headed by Howard Hilton in Lake Stevens, Washington was responsible for placing what is perhaps the World's smallest rendition of an osprey on a decimation filter integrated circuit utilized in signal analyzer instruments.

Snoopy - The silicon version of Snoopy illustrated in this section was discovered by Richard Piotter of New Ulm, Minnesota, who also loaned the 4-inch wafer (made by a 1980s-era semiconductor company named Trilogy) from which the image is derived.

The Con Artist - We found this guy in a trench coat trying to hock some fake Rolex watches (that are probably "hot") on a Hewlett-Packard PA-RISC microprocessor. Housed near the clock circuitry on the chip, the silicon artwork signifies a pun on higher-end microprocessor clock systems that utilize a more complex feature set.

Pac-Man - A silicon version of the famous game character was photographed gobbling the initials GAAS (gallium arsenide) on a TEMIC Semiconductors silicon-germanium radio frequency integrated circuit.

Milhouse Van Houten - Simpson's cartoon character Milhouse was spotted on a Silicon Image Sil154CT64 digital transmitter integrated circuit.

Godzilla - This mythical Japanese creature was discovered lurking on a pad within the Silicon Graphics MIPS R10000 microprocessor (this chip is sure crowded with silicon creatures).

Tux, the Linux Penguin - Tux is nesting within the pad ring on an integrated circuit of unknown function (perhaps the latest new microprocessor designed to run the Linux operating system).

Starship USS Enterprise - This famous Star Trek icon was discovered on a Texas Instruments bipolar logic integrated circuit.

The Pepsi Generation - Perhaps the smallest soft drink advertisement ever created, this 750 micron Pepsi commercial was discovered on a Hewlett-Packard CPU-support chip.

The Rolex - An intricate bitmap-like pattern of vias (interconnect shafts) was used to construct this incredible likeness of a Rolex wristwatch.

The Stay Puft Marshmallow Man - Coming to you from "GhostBusters", the Stay Puft Marshmallow Man was cooked in a frying pan within the circuitry of a Weitek math coprocessor designed in 1988.

Thor: God of Thunder - Probably the best silicon artwork we have yet seen, this image was discovered on a Hewlett-Packard graphics chip.

The Chip Smurf - An orange silicon Smurf is pulling a wagon containing the copyright symbol around the pad ring on a Siemens integrated circuit of unknown function.

Observing Mitosis with Fluorescence Microscopy - Mitosis, a phenomenon observed in all higher eukaryotes, is the mechanism that allows the nuclei of cells to split and provide each daughter cell with a complete set of chromosomes during cellular division. This, coupled with cytokinesis (division of the cytoplasm), occurs in all multicellular plants and animals to permit growth of the organism. Digital imaging with fluorescence microscopy is becoming a powerful tool to assist scientists in understanding the complex process of mitosis on both a structural and functional level.

Brightfield Microscopy Digital Image Gallery - Brightfield illumination has been one of the most widely used observation modes in optical microscopy for the past 300 years. The technique is best suited for utilization with fixed, stained specimens or other kinds of samples that naturally absorb significant amounts of visible light. Images produced with brightfield illumination appear dark and/or highly colored against a bright, often light gray or white, background. This digital image gallery explores a variety of stained specimens captured with an Olympus BX51 microscope coupled to a 12-bit QImaging Retiga camera system.

Polarized Light Microscopy Digital Image Gallery - As a contrast-enhancing optical technique, polarized light microscopy is unsurpassed in the magnificent array of colors and beautiful textures generated through interference between orthogonal wavefronts at the analyzer. Useful for observation of mineral thin sections, hairs, fibers, particles, bones, chemical crystals, polymers, and a wide variety of other specimens, polarized light can be employed for both quantitative as well as qualitative investigations. Visit this gallery to observe how polarized light can be of advantage in the observation of specimens that would otherwise exhibit poor contrast and be difficult to distinguish from the background.

Differential Interference Contrast Digital Image Gallery - Thin unstained, transparent specimens are excellent candidates for imaging with classical differential interference (DIC) microscopy techniques over a relatively narrow range (plus or minus one-quarter wavelength) of bias retardation. The digital images presented in this gallery represent a wide spectrum of specimens, which vary from unstained cells, tissues, and whole organisms to both lightly and heavily stained thin and thick sections. In addition, several specimens exhibiting birefringent character are included to demonstrate the kaleidoscopic display of color that arises when anisotropic substances are imaged with this technique.

Confocal Microscopy Digital Image Gallery - Scroll through serial optical sections from a wide variety of specimens, including tissue culture cells, thin and thick sections, and entire organisms, in this Java-powered image gallery.

The DNA Gallery - DNA undergoes a number of liquid crystalline phase transitions both in vitro and in vivo. This gallery explores the microscopic textures exhibited by various liquid crystalline DNA phases and their transition states.

The Phytochemical Collection - Acclaimed by Newsweek as being "better than Vitamins", phytochemicals are blazing a new frontier in the arena of cancer-prevention research. Explore the beautiful crystalline patterns displayed by phytochemicals captured in polarized light.

Intel Play QX3 Microscope Galleries - Check out digital images captured with this incredible microscope using contrast enhancing techniques such as polarized light, darkfield, brightfield, and Rheinberg illumination.

Phase Contrast Gallery - By "converting" phase objects such as living material into amplitude specimens, phase contrast illumination allows scientists to see details in unstained and/or living objects with great clarity and resolution. Explore the wide spectrum of biological specimens presented in this gallery of digital images.

Hoffman Modulation Contrast Gallery - The modulation contrast technique takes advantage of optical phase gradients to yield a pseudo three-dimensional effect on images seen in the microscope.

Darkfield Microscopy Gallery - Darkfield illumination provides good contrast for specimens that are often lacking in sufficient detail using other illumination techniques.

Dinosaur Bones - Photographs of thin sections made from bones left behind by dinosaurs that have been extinct for over 70 million years.

Electricity & Magnetism Interactive Java Tutorials - Visit our interactive tutorials on electricity and magnetism to explore how these two forces of nature operate in our everyday lives.

Building A Transistor - Explore how an individual Field Effect (FET) transistor is fabricated on a silicon wafer simultaneously with millions of its neighbors.

Pulsed Magnets - Pulsed magnets are among the strongest magnets in the world, and come in two forms: destructive and non-destructive. Of these two, non-destructive magnets are more suited towards scientific research, as they can reach some of the highest magnetic fields experimentally possible. This applet demonstrates how a non-destructive short pulse magnet works, and shows the relative field strengths generated.

How a Compact Disc Works - This tutorial explores how a laser beam is focused onto the surface of a spinning compact disc, and how variations between pits and lands on the disc surface affect how light is either scattered by the disc surface or reflected back into a detector.

Electrophoresis - Explore how electrical potential can cause migration and separation of macromolecules according to size in a cross-linked gel.

Mag Lab U: Learning about Electricity and Magnetism - Visit our sister website for more interactive Java tutorials, a timeline of historical events, a museum of antique devices, and articles on topics related to electricity and magnetism.