Groot is a sentient, tree-like individual and frequent accomplice of intergalactic criminal Rocket Raccoon. Together, the pair traveled the galaxy picking up bounties until they met Star-Lord and Gamoraon Xandar. Subsequently the four of them were captured and put in the Kyln, where they also met Drax. There, Star-Lord convinced them to assist him to sell the Orb for a massive profit and they managed to engineer a break-out and escaped. However, when it was discovered that the Orb contained one of the Infinity Stones which was being sought out by Ronan the Accuser, Groot convinced his friends to risk everything to stop Ronan's plans to destroy Xandar and enslave the world. During the war, Groot sacrificed his own life to save his new friends. However part of his destroyed body was planted by Rocket who regrew a new Groot, now called Baby Groot, as they joined the Guardians of the Galaxy.
As the new Groot slowly grew to the size of the original Groot, he stayed with the Guardians and endeavored with them on many adventures. Groot's tiny body and youthful innocence meant the Guardians spent much of their time trying to keep him out of harm's way. They were hired by the Sovereign to kill the Abilisk, a powerful multidimensional monster that was trying to devour the Anulax Batteries, which powered the planet. After being chased by the Sovereign to Berhert because of Rocket Raccoon who double-crossed them by stealing the batteries, they met Peter Quill's father Ego. He and Rocket, along with Yondu Udonta, were later captured by Taserface's faction of the Ravagers, but Groot was able to help them all escape. Groot then joined his allies and assisted them in destroying Ego and saving his friends, although Udonta lost his life during the battle. Remaining with the Guardians, Groot continued to grow and started exhibiting the personality of an adolescent.
He and Rocket Raccoon can be seen in the Oasis Nightclub.