Groot is a Flora colossus from Planet X. He was exiled from the planet when he killed one of his kind in defense of a maintenance mammal. While off-planet he found himself captured and imprisoned. In jail he befriended Rocket Racoon and was assigned to the team with Starlord.
As a member of «Guardians of the Galaxy», Groot is a powerful and versatile ally. He has on several occasions shown his ability to alter his size and shape, which often aids in the missions. His thick wooden skin makes him immune against normal gunfire. He is also able to regenerate himself and can regrow himself from a sprig if needed. He has a genius intellect, but the hardiness of his larynx makes it hard for others to understand him. People only hear him saying «I am Groot»