Intestinal smooth muscle cells. Coloured transmission electron micrograph (TEM) of a section through several smooth muscle cells from the intestines. The walls of the intestines contain bands of smooth muscle that contract to push food through the digestive system. Structures seen here include cell nuclei (brown-white), mitochondria (green) and the basement membranes surrounding the cells (thin, orange). Magnification: x5000 when printed at 10 centimetres across.