I created this image of a mouse 3T3 fibroblast using an Olympus microscope and ImageJ. I stained the cells with DAPI and rhodamine-phalloidin, took two separate images and overlayed them in ImageJ. DAPI is a fluorescent dye that binds to DNA, revealing the cell nucleus, which I have colored green in this image. Phalloidin is a mushroom toxin that binds to filamentous actin, a major component of the cytoskeleton. In this preparation, the phalloidin molecules are bound to rhodamine, another fluorescent dye, which is colored red here. Rhodamine and DAPI fluoresce at different wavelengths, allowing the microscope camera to take separate images of the nucleus and the actin cytoskeleton. By changing the color filter without moving the microscope slide, I was able to take two pictures and then combine them in ImageJ, changing the colors and adjusting the brightness and contrast of each dye independently. I was also able to adjust the colors. Rhodamine produces a red fluorescence and the color seen here is essentially what you see when looking through the microscope. DAPI, however, is blue, but I colored it green in ImageJ.