Peroxisomes are small, membrane-bound organelles that were discovered in 1965 by Christian de Duve. Present in almost all eukaryotic cells, these organelles were named for the hydrogen peroxide they produce as an intermediate in the process of normal cellular metabolism. Through the use of the enzyme catalase, peroxisomes are also responsible for detoxifying cellular metabolic side products by converting the hydrogen peroxide they generate into water and free oxygen molecules. Peroxisomes, which contain more than 40 oxidative enzymes, are also associated with many other cellular activities, such as lipid degradation and the synthesis of various biochemicals. Proteins intended for peroxisomes are manufactured in the cytosol and then transported into the organelles, which undergo fission to produce more peroxisomes when their size increases to a certain level.

Histones present in the nuclei of cancerous bone cells (U-2 OS line) presented above were immunofluorescently labeled with primary anti-histone mouse monoclonal antibodies followed by goat anti-mouse Fab heavy and light chain fragments conjugated to Cy3. In addition, the specimen was simultaneously stained for filamentous actin with Alexa Fluor 350 conjugated to phalloidin, and for peroxisomes with Cy2 conjugated to goat secondary antibodies that target rabbit anti-PMP 70 (peroxisomal membrane protein). Images were recorded in grayscale with a QImaging Retiga Fast-EXi camera system coupled to an Olympus BX-51 microscope equipped with bandpass emission fluorescence filter optical blocks provided by Omega Optical. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles.