Jean Grey-Summers was born the daughter of Dr. John Grey and Elaine Grey. Before joining the X-Men, she lived with her family in Annandale-on-Hudson, New York, where Dr. Grey worked as a history professor at Bard College.
Jean is the only member of her immediate family with mutant abilities (her niece and nephew, Joey and Gailyn, are also revealed as mutants). Her powers first manifest at the age of ten, prematurely triggered when her best friend, Annie Richards, is hit by a car. As her friend lies dying, Jean instinctively links to her mind and senses what Annie feels when she dies; the trauma of experiencing her friend's death nearly kills Jean as well, but instead leaves her in a coma.
Jean's parents seek the expertise of specialists to rouse her out of her catatonic state, of which only Professor Charles Xavier is able to help. Xavier uses Jean to help locate mutants with his Cerebro Machine. During one fateful session on the astral plane Jean senses young Scott Summers in the orphanage and an aspect of her mind, manifesting in the form of a golden Phoenix raptor, reaches out to him. Xavier realizes that Jean's young mind cannot yet cope with her abilities, so he telepathically blocks her access to them, allowing her powers to evolve at a more natural pace. Jean develops her telekinetic powers at the age of 13. As a teenager, Jean leaves her parents to attend Xavier's School for Gifted Youngsters and, using the codename "Marvel Girl", becomes the first female X-Man. While on a mission that took them into space Jean is observed by the Phoenix Force which is drawn to Jean's unlimited potential. Jean envisions her transformation into Phoenix but within an instant she cannot remember what she foresaw.