A species of microscopic (1 mm), transparent round worm found in the soil (see figure below), and used for genetic studies as it has a small genome of only six chromosomes, about 3000 genes, few cell types and thus a relatively simple nervous system. It is ideally suited for research in developmental genetics as it only has a 16-hour period of embryogenesis in a petri dish. It was the first multicellular organism to have its genome sequenced, something that was achieved in 1998.
