Spleen cell. Coloured transmission electron micrograph (TEM) of a section through a cell in the spleen, an organ located in the upper left side of the abdomen in vertebrate animals. This organ contains tissues known as red and white pulp, consisting mainly of white blood cells and red blood cells. The spleen cells themselves form a loose reticular network within which the two types of pulp are contained. Magnification: x3200 when printed at 10 centimetres wide.