The original Firestorm was distinguished by his integrated dual identity. High school student Ronnie Raymond and Nobel Prize-winning physicist Martin Stein were caught in a nuclear accident that allowed them to fuse into the "nuclear man" Firestorm. Due to Stein's being unconscious during the accident, Raymond was prominently in command of the Firestorm form with Stein a voice of reason inside his mind. Banter between the two was a hallmark of their adventures. Initially Stein was completely ignorant of their dual identity, leaving him concerned about his unusual disappearances and blackouts, but Ronnie was eventually able to convince him of the truth, allowing them to bond as separate individuals rather than as parts of a whole. By the series' 100th issue, Stein learned that he was destined to be the true Fire Elemental and would have been were it not for Ron Raymond also being there by circumstance. Raymond and Arkadin were returned to their old lives, and Stein as Firestorm was accidentally exiled to deep space in the process of saving the Earth. He thereafter spent many years traveling through space as a wanderer, returning to Earth on only two occasions: the War of the Gods crossover event, and again in the JLA spin-off, Extreme Justice #5, where Stein cured Raymond of his leukemia and allowed Raymond to retain the original Firestorm persona on his own.
Professor Martin Stein is played by Victor Garber. He was working on his Firestorm project with his student, Jason Rusch (played by Luc Roderique), right outside S.T.A.R. Labs when the Particle Accelerator exploded. The explosion caused him to combine with Ronnie Raymond, an employee at S.T.A.R. Labs, into the Firestorm Matrix. They had gone missing for several months until Caitlin Snow and Cisco Ramon find them combined in Ronnie's body. General Wade Eiling has been after the Firestorm project to use it as a weapon for the military. The Flash and the S.T.A.R. Labs team are able separate Martin and Ronnie but they decide to recombine as the nuclear hero, Firestorm. They defeat General Eiling as well as team up with the Flash and the Arrow to take down the Reverse Flash. At the end of Season 1, Ronnie sacrifices his life to save Central City from being swallowed by a black hole. During Season 2, Martin starts getting sick from not turning into Firestorm and needs a new partner to combine with. The only compatible people were Henry Hewitt and Jefferson "Jax" Jackson. Jax initially turns him down. Henry is excited about becoming Firestorm but he wasn't compatible enough so they went with Jax. The Firestorm Matrix had an effect on Henry, changing him into the nuclear villain, Tokamak. Martin and Jax then combine into the new Firestorm and team up with the Flash to defeat Tokamak.
Victor Garber reprises his role as Martin Stein. He and Jax had been enlisted as the new Firestorm by Rip Hunter to go back in time to stop Vandal Savage from rising in power and taking over the world in the year 2166. The other members of the team include Hawkman, Hawkgirl, the Atom, White Canary, Captain Cold and Heat Wave. It is revealed during the series that Ray Palmer used to be one of his students. In a trip back to the 70's, Stein, Jax and the White Canary run into a young Martin Stein. They need to take one of his old inventions to track a piece of the Atom's suit that was lost. They later realize they need to make sure he goes to a party so he can meet his future wife, Clarissa. It almost fails but Rip makes sure that time doesn't get altered.