When a mosquito bites a healthy human being, the sporozoites (infectious form) are injected into the body. They reach the liver and start multiplying and forms merozoites in liver cells. They rupture the liver cells and escape into the blood stream. They digest human blood and produce a toxic metabolic waste called haemozoin. They digest haemoglobin and release high quantities of free heme which is toxic to cells, so the parasites convert it into an insoluble crystalline form called haemozoin. Then, merozoites infect red blood cells, and the parasites multiply asexually, to develop into ring forms called trophozoites .