Turritopsis nutricula is a hydrozoan (jellyfish) with a life cycle in which it reverts back to the polyp stage after becoming sexually mature. It is the first case in which a metazoan (animal) is capable of reverting completely to a sexually immature, colonial stage after having reached sexual maturity as a solitary stage. It does this through the cell development process of transdifferentiation. This cycle then repeats. Thus, it appears that it has cheated death and is a potentially immortal, solitary metazoan.