Coloured transmission electron micrograph (TEM) of epithelial cells from the tongue of a pig. Epithelial cells are flat and line all of the body's surfaces, cavities and lymph and blood vessels. The cell junctions between cells are prominent. Cell nuclei, which contain the cell's genetic information in the form of DNA (deoxyribonucleic acid), are orange. Magnification: x4,200 when printed at 10 centimetres wide.