Confocal light micrograph of cultured MDCK (Madin-Darby canine kidney) epithelial cells. Epithelial cells are flat and line all of the body's surfaces, cavities and lymph and blood vessels. Actin, which is part of the cytoskeleton, is stained magenta. Cell nuclei, which contain the cell's genetic information in the form of DNA (deoxyribonucleic acid), are blue. The Golgi apparatus, which modifies and packages proteins, is green. Magnification: x1,200 when printed at 10 centimetres wide.