Malaria-infected red blood cells. Coloured scanning electron micrograph (SEM) of red blood cells (erythrocytes) with the gametocyte stage (green) of the malaria parasite. The Plasmodium parasite that causes malaria goes through several stages in its life cycle, involving liver cells and blood cells. The sporozoite stage is injected into humans by a mosquito. After developing in liver cells, merozoites are released that infect red blood cells. The trophozoite stage in red blood cells digests the haemoglobin in the cells, causing anaemia in the host. Asexual replication releases merozoites that invade other red blood cells. Sexual reproduction (seen here) releases gametocytes. Magnification: x4000 when printed at 10 centimetres across.