Caitlin Snow is an M.D., specializing in genetics, who works at Star Labs. Since Barry Allen became the Flash, she has worked as part of his support team. During this period, she was briefly reunited with her former fiance, Ronnie Raymond, who had become Firestorm. As of mid-2016, she has become aware of a dark side within herself. However, this deeply troubles her, and for now she shows no enthusiasm for embracing evil.Her Earth-2 doppelganger has a very different history: After gaining the ability to absorb heat from living beings and to project cold and ice, Caitlin Snow emerged a changed woman and became the villain Killer Frost. Sociopathic by nature, Killer Frost's icy exterior matched her chillingly cold interior. She seemed to thaw slightly during an encounter with the Earth-1 Flash and his companions, but only temporarily. Ultimately, she betrayed Zoom, and paid with her life.Note: Since Flash characters exist in a world of time travel and alternate realities, the life histories described here might become radically out of date at any time.