Mimivirus is a type of giant virus that was first discovered in 2003. It is notable for its large size, which is comparable to some bacteria, and its complex structure. Mimivirus infects amoebas, particularly Acanthamoeba, and can be found in various environments, including water and soil. This virus has a unique genome that contains many genes previously thought to be exclusive to cellular organisms. Mimivirus challenges traditional definitions of viruses, as it exhibits characteristics similar to living cells, such as the ability to replicate and produce proteins. Its discovery has expanded our understanding of viral diversity and evolution.