Intestinal protozoan parasites in cell. Coloured transmission electron micrograph (TEM) of several Encephalitozoon intestinalis protozoan parasites (yellow and red). This parasite is one of several known as microsporidia. The microsporidia inject themselves into a host cell, where they replicate and pass through several stages, ending with the formation of spores that infect new cells. Many areas of the body can be affected, but the common site of infection is the intestines. Infection, by ingestion of contaminated food or water, can cause severe diarrhoea in humans. Magnification: ×10,400 when printed 10cm high.