Viruses are often thought of as being tiny, but some are relatively huge and may have actually descended from cells. The giant mimivirus Acanthamoeba polyphaga mimivirus, for example, is some 400 nm across. Discovered in 2003, it has many genes previously thought to be unique to cellular life, but it was an open question as to whether it might have stolen them from some sort of cell. Jean Michel Claverie of the Structural and Genomic Information Laboratory in Marseille and colleagues have now found a huge new virus in sea water off the coast of Chile. The discovery of Megavirus chilensis – which seems to be a distant relative of the mimivirus and shares its cell-like genes – bolsters the case that at least some viruses had cells as ancestors.