This incredible scanning electron micrograph shows the reproductive cells, called oocytes, of a malaria parasite developing on a mosquito's intestinal wall. Malaria parasites are protists and members of the genus Plasmodium. In humans malaria is caused by several species, of which P. vivax is the most common and P. falciparum the most deadly. This image actually shows a species that infects rodents. When these oocytes rupture, they release sporozoites that travel to the mosquito's salivary glands. From there, they can infect a vertebrate host.