This scanning electron micrograph (SEM) of a Trypanosoma brucei brucei parasite showing a replicating bloodstream trypomastigote. On transmission to a new host, parasites divide rapidly to help the population become established. The two flagella on this parasite indicate that it is undergoing the process of cell division. Trypanosoma brucei brucei is a parasite that causes sleeping sickness. Supplied by Sue Vaughan, courtesy of Wellcome Images.