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 and a three-color liquid crystal tunable filter.

Amphibian Skin - Due to their habitation of both terrestrial and freshwater locales at various stages in their life cycle, amphibians have a unique kind of permeable skin. Both oxygen and water are allowed to pass in and out of the delicate integument in order that homeostasis and a sufficient level of respiration may be maintained at all times, even when the animal is underwater. The skin of amphibians is also unusual because it must be kept in a relatively moist to help draw oxygen through the skin. In order to sustain the necessary moisture level, amphibians secrete mucus via glands contained in the skin.

Bacteria, Yeast, and Blood - Despite the proliferation of antibacterial soaps and cleaners over the last decade, most bacteria are harmless or beneficial to humans. Indeed, the tiny organisms are significant contributors to the economies of many countries, aiding in the pickling, fermentation, and curing of a large number of products. Bacteria are also extremely valuable in the laboratory and have been utilized heavily in genetic research. Some bacteria are, however, pathogens that can cause disease in humans and other animals. These organisms are particularly adept at avoiding the body’s defense mechanisms once inside the bloodstream.

Bald Scalp - The primary cause of baldness is a genetic disposition that typically leads to the receding of the hairline at the front of the head or the thinning of the hair along the crown. Though this hereditary condition is usually referred to as male pattern baldness, women may also carry the trait. Yet, females are not as susceptible to the physical manifestation of the genetic disposition because it is usually only exhibited in the presence of the male sex hormone testosterone.

Bracken Fern (Pteridium) Rhizome - Although modern ranchers and wildlife managers often consider bracken ferns a nuisance, they may be utilized by humans in a variety of ways. In fact, they were so valued in the Middle Ages, when they were commonly used as a source of fuel and as a roofing material, that they could be used as a sort of currency. Bracken ferns were also widely used at one time in the production of potash and bleach, and continue to be utilized in some locales as a food source and as bedding for cattle.

Cerebrum - Today, the vast majority of the brain’s weight (about 85 percent) is dedicated to the cerebrum. In early man, however, the cerebrum was not as well developed, consisting of only about a third of its current weight. This significant physical change has been accompanied by important changes in the mental processes, humans becoming increasingly capable of more and more complex activities over time. Indeed, most scientists believe it is the relative size of the cerebrum that most differentiates humans from other animals, since it is considered the origin of all conscious activity.

Clubmoss (Lycopodium) Strobilus - Though typically found in modern times creeping along forest floors or tropical mountains, clubmosses were once one of the most prevalent types of plants on Earth. During the Carboniferous period, clubmosses could achieve massive heights, growing as tall as some trees and contributing greatly to the layers of organic material that would eventually develop into the coal deposits commonly used as a source of fuel today. Modern members of Lycopodium are greatly reduced in size from their ancestors, a common variety such as stag’s horn moss only growing about four inches high and ten feet long.

Ductus Deferens - Thick-walled, the ductus deferens is composed of several layers of tissue. Then innermost layer is a folded mucous membrane that is always moist. Encircling this layer are three layers of muscle tissue, which provide the tube with the ability to contract, a necessary action for the conveyance of bodily fluids and sperm. As the ductus deferens rises upwards from the epididymis towards the bladder, it also comes to be surrounded by nerve fibers, arteries, and veins, and the complex structure further encased in connective tissue is referred to as the spermatic cord.

Epididymis - The epididymis, which receives a constant supply of blood from a branch of the testicular artery and is divided into three basic regions, is believed to function in multiple ways. The largest part of the epididymis, known as the head, is located atop the testis, while the smallest part, commonly called the tail, is located where the epididymis separates from the gland. Of intermediate size is the body, which is attached to the rear of the testis and spans its length. The head and body of the epididymis are essential for the maturation of sperm and the tail serves as a storage site for the reproductive cells.

Fern Spores - Fern spores are typically covered in a thick cell wall, but may exhibit a wide variety of characteristics, many of which play a critical role in determining the taxonomic classification of species. The basic shape of these reproductive cells may, for instance, be either tetrahedral or bilateral, while their walls may be either smooth or variously patterned. The reason for the diversity of spores in such regards is not fully understood by modern scientists, many of the differences that occur among the cells seeming to have no functional purpose.

Frog Ciliated Epithelium - Ciliated epithelial cells are a variety that exhibit small, hairlike projections. Layers of these cells comprise ciliated epithelium tissue, which can be found in a number of locations within the body. Ciliated epithelium tissue typically lines the bronchi of the lungs, the trachea, regions of the nasal pathways, and reproductive organs of both males and females. The cilia of the tissue are provided energy by mitochondria and their movement helps transport substances, such as mucus, through these regions.

Frog Striated Muscle Tissue - Attached to the body’s skeleton via flexible tendons, striated muscles are usually arranged in pairs. Each member of a pair of pulls in the direction opposite of the other one, providing precise control of the skeletal structure. For instance, the biceps are responsible for flexing the forearm and the triceps are responsible for extending the same part of the body. The contraction of striated muscle is stimulated by electrical impulses sent out by the nervous system and requires energy from ATP.

Heavily Pigmented Skin - In humans, melanins are largely responsible for the relative darkness of the skin, as well as the hair and the irises of the eyes. High levels of localized melanin are also the cause of freckles and moles. The amount of melanin pigments in the body are usually a function of genetics, but may be altered by various means. A suntan, for instance, is an indication of the overproduction of melanin caused by exposure to ultraviolet light. Certain disorders, such as Recklinghausen’s neurofibromatosis, which involves the improper storage of melanin in melanocytes, can also cause unusually high levels of pigmentation.

Hemlock Leaf - The hemlock tree typically found in western North America is T. heterophylla, also known as Prince Albert’s fir and hemlock fir. Trees of this species are the tallest in the genus, often growing as many as 200 feet high. Lumber derived from them is superior to that of other hemlocks and is comparable in quality to pine. The wood of the western hemlock was formerly utilized heavily to construct sugar and flour barrels since it is free from resinous materials, but is used more often today for paneling, boxes, crates, and general construction.

Horsetail Strobilus - Horsetail plants have a very ancient lineage that extends back some 200 million years. Similar to other primitive vascular plants, they exhibit an asexual reproductive structure, the sphenophyte strobilus, more commonly known as a cone. Unlike the better-known pinecone, however, the strobili of the horsetail plant may only contain one type of spore since they are homosporous. Horsetail cones, each of which encases many sporophylls within a single sporangium or case, form along the uppermost region of the plant’s branches.

Human Cerebral Cortex - In humans, the cerebral cortex is significantly larger than in other animals of similar size. Typically one to four millimeters thick with an approximate surface area of 2,000 square centimeters, the only way the sizable region of the brain can fit into the human skull is by folding extensively. The convolutions of the cerebral cortex are usually referred to in terms of sulci and gyri, which are respectively fissures and crests along the surface of the brain.

Immature Testes - During embryonic development, the testes originate in the abdomen near the kidneys. Late in the developmental process, around the seventh or eight month of pregnancy, the glands move into their lower position within the scrotal sac. This change of position is regulated by the male sex hormone testosterone, the secretion of which is stimulated by the hormone called chorionic gonadotropin exuded by the placenta. Occasionally, the testes do not descend properly, remaining within the abdomen even after birth. In such cases, medical treatment is usually necessary in order to avoid sterility.

Keloid Scar Tissue - A keloid is a type of swollen scar that grows much larger than other scars, appearing similar to a fibrous tumor. Keloids are not especially dangerous, but they may cause discomfort and itching and may limit movement if they become too large, especially if they are located around the joints of the body. In some cases, they may be severely disfiguring as well. Similar to other types of scar tissue, keloids usually require medical treatment in order to improve their appearance, although there are documented cases of them diminishing in size on their own.

Mammalian Cardiac Muscle Tissue - Comprised of elongated cells with multiple nuclei, cardiac muscle tissue appears striated under the microscope. Yet, unlike other striated muscles in the body, cardiac muscle controls an involuntary action, similar to smooth muscle tissue. The rhythmically contracting cardiac muscle tissue is essentially under the control of the heart’s pacemaker, the sinoatrial node. However, a number of chemical substances may affect the action of the tissue, many of which are utilized for medical purposes.

Mammalian Cerebellum - The two lateral hemispheres of the cerebellum are each composed of three different lobes that evolved at different times. The earliest to develop was the flocculonodular lobe, which is intricately involved in the maintenance of balance. The next region of the cerebellum to evolve was the anterior lobe, a structure that is responsible for receiving sensory information from the spinal cord. The posterior lobe, which accepts nerve impulses from the region of the brain called the cerebrum, was the last part of the cerebrum to evolve.

Mammalian Hyaline Cartilage - Hyaline cartilage is the most prevalent of three types of cartilage found in humans and other vertebrates. It is also the type of the connective tissue that forms the embryonic skeleton. Bluish-gray, pearly, and semitranslucent, hyaline cartilage contains a large number of collagen fibrils dispersed in random directions and a relatively small amount of elastin. It is, therefore, very resilient, but not as flexible as elastic cartilage, which contains significantly greater amounts of elastin.

Mammalian Graafian Follicle - During the youth of a female, several hundred thousand graafian follicles may be present in the ovaries, each of which contains an oocyte surrounded by a single stratum of cells. By the time puberty is reached, however, most of these follicles have deteriorated and collapsed. Those that remain develop to maturity one at a time in a monthly cyclical process. A substance called the follicle-stimulating hormone that is emitted by the pituitary gland is the factor that facilitates the beginning of this process, ensuring the follicles growth and maintenance.

Mammalian Kidney - The kidneys of mammals are somewhat different than those of reptiles, birds, and other animals, which are comprised of numerous small lobules. In mammals, each of the organs may be considered to be divided into two primary parts: the cortex and the medulla. The cortex of the mammalian kidney is granular in appearance due to the many tubules and glomeruli it contains. The inner medulla, however, is basically smooth, although some striations are present.

Mammalian Smooth Muscle Tissue - Smooth muscle is typically comprised of numerous elongate spindle-shaped cells, each of which contains a single nucleus located in its center. As indicated by its name, the tissue displays no striations or other distinct patterns under the microscope. The contraction of smooth muscle is slow and generally under the control of the autonomic nervous system, resulting in its alternate moniker, involuntary muscle. Most of the body’s hollow internal organs, including all of the parts of the digestive system, are lined with smooth muscle.

Mammalian Testes - The human testes are oval-shaped organs that weigh about 25 grams each. Though only about two inches long and one inch in diameter, each of these reproductive glands is comprised of approximately 800 seminiferous tubules. In younger individuals, the tubules typically exhibit a simple shape, but after sexual maturity is reached, the structures become branched and coiled. The fully developed tubules are capable of generating sperm through the stimulation of the spermatogonia, or sperm-producing cells.

Marchantia Liverwort Archegoniophore - The thallose liverworts that have been most heavily researched belong to the genus Marchantia, which are commonly found among moist soils in the Northern Hemisphere. In their sexual stage, these plants are dark green, dichotomously branched, and ribbon-like, typically growing about a half-inch wide and several inches long. When they are sexually mature, they may either grow small umbrella-shaped male reproductive organs, known as antheridiophores, or female archegoniophores, the shape of which is reminiscent of miniature palm trees.

Oleander Leaf - Though the appearance of oleanders varies by species, most exhibit thick, lance-like leaves and beautiful flowers that develop in clusters. These flowers generally bloom in the spring and may appear in a variety of colors, including pink, red, yellow, apricot, and white. Hardy and fast growing, oleanders are widely utilized in landscaping, especially in cities and along highway medians, despite the fact that they are extremely poisonous. The toxin present in oleanders is most concentrated in the shrub’s sticky, milky sap, but is contained in smaller quantities in all its many parts.

Optic Nerve - Each optic nerve contains approximately one million nerve fibers, a number substantially lower than the more than one hundred million receptors that are located in the retina. Thus, it is generally assumed that a significant amount of information processing takes place within the retina, greatly decreasing the number of signals that must be transferred to the brain via the optic nerve. Yet, any damage to the optic nerve may be as detrimental to one’s sight as an injury to the retina.

Palmar Skin - Palmar skin is attached to a sheet of tissue called the palmar fascia that underlies it by septa. This connection serves to help stabilize the skin, making the palms better suited for grasping various objects. Sometimes, however, the palmar fascia thickens, resulting in a condition known as Dupuytren’s disease. Symptoms of the condition include the appearance of nodules and pits in the skin of the palms, as well as a general thickening of the integument. In severe cases, thickened cord-like structures may also occur and extend into the fingers.

Pine Needle - In addition to the better-known commodities generated from pine trees, a number of useful, but less profitable items can be made from the needles of the evergreens. Some Native Americans, for instance, utilized the narrow leaves to brew a type of tea that they utilized as a form of medical treatment. Certain tribes also gathered shed pine needles from the ground in order to use them to weave baskets, a practice that is still carried out today in some parts of the world. Pine needle are perhaps more popular, however, in modern times as a source of aromatic oil and as a mulch for landscaping and farming.

Pine Stem - Pine is the common name for any tree belonging to the genus Pinus of the family Pinaceae, the largest of all families of conifers. Commercially valuable, pines are heavily grown as both ornamentals and timber trees, over 50 different species of the trees being cultivated in the United States alone. Chiefly found in northern temperate regions, most pines exhibit woody stems covered by bark, which helps protect the inner tissues that conduct water and nutrients from the roots of the trees to the leaves.

Plantar Skin - Comprised of five morphologically distinct cellular layers, plantar skin is well designed to protect the feet from injury. Indeed, some studies have shown that the skin along the soles of the feet can withstand immensely greater amounts of abrasion or chafing than the skin along most other parts of the body before the pain threshold is reached. Reports also indicate that plantar skin is somewhat resistant to puncture, the integument attempting to shape itself around any sharp objects it comes into contact with.

Prostate Gland (Older) - Following puberty, the prostate gland is about the size of a walnut for much of a man’s life. However, around the age of 40 or 50, the prostate often begins to enlarge, a process referred to as benign prostatic hypertrophy (BPH). The reason for this physiological change is not completely understood, but is believed to involve a number of factors, such as increased levels of the female sex hormone estradiol and greater production of dihydrotestosterone, a derivative of the male sex hormone testosterone.

Prostate Gland (Younger) - The development of the prostate gland is dependent on the hormones produced by the testes. In infants, the organ is extremely small, approximately the size of a single grain of wheat. During puberty, which usually occurs in males between the ages of 10 and 14, the prostate enters a period of accelerated growth and typically achieves its mature size. However, the prostates of boys who are castrated before this stage in their life never reach their full functioning capabilities or adult dimensions.

Pseudostratified Ciliated Columnar Epithelium - Unlike the epithelium of the skin, a pseudostratified ciliated columnar epithelium appears to have multiple layers, but is actually only comprised of a single sheet of cells. The positioning of the nuclei within the individual columnar cells causes this illusion. These structures, which are easily identifiable with the help of a microscope, are found at various levels, creating a stratified appearance. A microscope also facilitates the observation of the tiny hairlike cilia that line the cells. Found most heavily along the respiratory tract, pseudostratified ciliated columnar epithelial cells help trap and transport particles brought in through the nasal passages and lungs.

Salamander (Amphiuma) Liver - Amphiuma is a genus of aquatic salamanders that have very small limbs and are sometimes misidentified as snakes or eels. Indeed, members of the genus, which may grow up to three feet long, are often better known by the name Congo eel or Congo snake. These salamanders spend most of their time burrowing through mud and debris searching for insects, mollusks, frogs, and other small prey, but they can also be dangerous to larger animals. Their teeth are quite sharp, their jaws are strong, and their bite can be brutal.

Simple Columnar Epithelium - Columnar epithelium can be found along the intestinal tract, spanning from the end of the esophagus to the rectum. This type of tissue also occurs in the ducts of various glands. Epithelial cells are taller than they are wide and contain nuclei along their bases. The membranes that surround them are relatively thin, but can be easily viewed with the aid of a microscope. One of the best-known examples of columnar epithelial cells appears as a covering of the projections called villi found in the small intestine.

Thyroid Gland - Though the specific effects of the hormones secreted by the thyroid are various, their most important role in adults is regulating metabolic processes. In children, thyroid hormones also play an essential role in proper growth and development. Thus, a deficiency in thyroid secretion in childhood is associated with both dwarfism and mental deficiencies. Goiter, a disease characterized by the enlargement of the thyroid gland to such an extent that a sizable lump appears at the front of the neck making swallowing and breathing difficult, is also caused by inadequate levels of thyroxine.

Zamia Stem - Plants of the genus Zamia are primarily found in tropical areas of the Americas, though some also occupy subtropical regions. Indeed, these cycads were once important to many Native American tribes, especially the Seminoles that inhabited parts of Florida. The Seminoles called the plants coonties and often dug up their starchy, turnip-like stems for practical use. After washing them and cutting them into pieces, the stems were typically pounded into a powder. This powder was then repeatedly washed in water so that the starch would separate, resulting in a pasty substance that was fermented and dried back into a powder. The final substance, which today is sometimes referred to as Florida arrowroot, was a diet staple commonly utilized in a manner similar to flour.

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