Justice League: A Better World
Ronnie Raymond/Martin Stein
Firestorm is a nuclear-powered super-hero with the ability to transmute elements. The Firestorm Matrix is a composite of multiple people bonded together, originally high school student Ronnie Raymond controlling the body and nuclear physicist Professor Martin Stein giving direction as an additional consciousness.
Ronnie was brash and fun-loving. He didn’t take having the Firestorm powers very seriously at first, but eventually grew to the responsibility. Martin provided a balance to Ronnie’s energetic personality, preferring to analyze the situation and think through any problems. Together, they made a very effective team.
DC Wikia entry