- "Yeah, you're arrogant... but you're also smart and kind and selfless. You want to make the world a better place and you're willing to risk everything to make that happen... that is not a bad guy. And neither is this one. "
- —Jefferson Jackson to Martin on his past and present[src]
Professor Martin "Marty" Stein (born March 16, 1950) is a physicist who was the team leader for the F.I.R.E.S.T.O.R.M. project. He co-wrote a paper on it with Jason Rusch. After the S.T.A.R. Labs particle accelerator exploded he became one half of the transmuted and conjoined meta-human Firestorm alongside Ronnie Raymond. Firestorm was resurrected with Jefferson Jackson as the second half after Ronnie's death. In early 2016, Martin Stein was recruited by the rogue time-traveler Rip Hunter on a mission to take down Vandal Savage.
Life prior to the accelerator's malfunction
Martin Stein was born into the Jewish faith and his father made him become a rabbi directly before Martin's enrollment at MIT. Martin Stein attended University of Chicago where he became classmates with Quentin Quale, as they were both of class of '70. Their relationship could be seen as more than mere acquaintance, for Martin was the only person with whom Quentin shared the truth about his brother's death being a suicide.
In October 1975, the visit of his future self causes him to miss a faculty mixer arranged by his future wife's uncle who was a professor at Ivy Town University. However Rip Hunter is able to "encourage" him to attend the mixer, thus preserving the timeline. 
Martin accomplished various achievements in the scientific field and even had a table for all the awards he received, though his wife Clarissa would remark that perhaps he was just a tad too focused on his career. However, Martin still loved Clarissa very much, and often spoke of his affection for her when conversing with his friends. He wrote numerous papers on a vast array of scientific theories, a number of which were for the Oxford University Press; one of them was about the topic of time travel, published around 1990, and became well known in certain circles.
Professor Stein worked as the leader of the F.I.R.E.S.T.O.R.M. project. He published an 800-page paper regarding the project that was co-written by Jason Rusch. Wishing to get help for it, he went to an unspecified source.
The day of the accident at S.T.A.R. Labs and afterwards
39 years later Martin Stein was on the train back to Central City, the same train Barry Allen rode from his trip back from Starling City. They both interacted, discussing the theories of Albert Einstein. They mentioned the brilliance of Einstein(he might be the only person in the entire Arrowverse that is more intelligent than Eobard Thawne)and Barry's own girlfriend problems.
That night, Martin was near S.T.A.R. Labs and happened to be in the middle of an anti-particle accelerator protest. With the accelerator on, he dropped his Firestorm Matrix and the wave (containing particles of Ronnie Raymond) hit him, fusing the two together. Martin Stein was considered "missing" ever since.
One month later, Stein (in Ronnie's body) found himself trashed. He went back to his wife, who obviously could not recognize him as he took on the appearance of a stranger, forcing him to flee from their house and live on the streets.
9 months later Close to the one year anniversary of the S.T.A.R. Labs incident, Ronnie's subconscious loosely gained minimal control of his own body and revealed himself (with Stein still the prominent conscious) to Caitlin Snow. Afterwards Caitlin and Cisco Ramon became persistent on finding Ronnie, not knowing that Martin was the one in most of the control of Ronnie's body. They wanted to help him but he refused. Later when The Flash was about to be killed by the Reverse-Flash, Stein came to his aid by blasting the speedster off of him. He then told Caitlin not to look for him again before flying off.
3 months later Stein is still in Ronnie's body then later came to his old schoolmate Quentin Quale asking him for help but ended up losing control of his powers and severely burned Quale to a critical condition. Team Flash eventually tracked him down and managed to persuade him to come in, thanks to Clarissa. As the team did test on Stein, they discovered that Ronnie's body was becoming unstable and that he would eventually explode. Hearing this, Stein traveled as far as he could from the city to avoid harming anyone. Caitlin and Barry tracked him down and tried to prevent him from exploding by putting a device on his chest, which didn't seem to work at first, as the explosion still happened with Barry and Caitlin barely escaping the blast.
They succeeded in separating. However, Martin and Ronnie maintained synchrony in their brain waves, enabling them to communicate telepathically to a degree. General Wade Eiling eventually sought to kidnap both of them to experiment on, succeeding in kidnapping Martin. Ronnie sensed Martin being in danger, used a piece of broken glass to crave a message, hoping Martin would receive it; he did, and in return, sent a Morse code respond to share the location where he was kept captive, thus Barry and Ronnie went to rescue Martin. While Barry was occupied, Martin and Ronnie were cornered, and forced to merge. However, this time, having accepted each other and achieved balance, both of their minds were active on a conscious level. Although Ronnie was in control of the Firestorm body this time, Martin was still active to communicate with one another telepathically. With the use of the device, they were able join and separate at will and separated after the incident. Ultimately, they chose to visit a colleague of Martin Stein's in Pittsburgh to get a better understanding of their condition. Having decided this, they joined again to become Firestorm and flew off.
3 months Later when Barry realized he was too slow for the Reverse-Flash he called Firestorm and Oliver Queen / The Arrow to help him in his upcoming fight against him. When Wells arrived at S.T.A.R. Labs to use the particle accelerator the Flash confronted him and Firestorm and Arrow soon joined him, but Wells was unimpressed and fought all 3 of them. When Flash was down Firestorm distracted Reverse-Flash so Arrow could shoot him with a special arrow to disable his speed, but Reverse-Flash used his tornado powers to send Firestorm blocks away. Flash quickly recovered him and stopped him falling to his death and resumed the fight shooting a massive ball of fire at Reverse-Flash atop S.T.A.R. Labs when Flash lead him up there, causing him to fall on a car where Arrow finally finished him off with an arrow and made him pass out. Having defeated the Reverse-Flash, the Arrow parted ways with Flash while Firestorm remained.
While incarcerated inside the Particle Accelerator, Eobard Thwane revealed his plan of having Barry Allen opening up wormhole inside the accelerator in order for him to time-travel back to the future. Eobard proposed that when the wormhole opened, Barry should use it to travel back to the night when his mother got killed and prevent her assassination. Hearing this proposal, Martin discussed the complications, calming that if Barry does decide to prevent Nora's death then his entire life and all of the current history up to that point would be completely erased and Barry would never have met all the people in his new life as The Flash. However, Martin remained uncertain of the full extent of the repercussions.
Doctor Stein began analysing the variables of the wormhole in order to verify Thawne's claims, working alongside Eobard's distant grandfather, Eddie Thawne. Eddie immediately felt unqualified to help so he decided to leave, but he was stopped by Martin who said that he is equally important as anyone else. Eddie gave a rebuttal by mentioning Eobard's claims about the future, how Eddie failed to accomplish anything in his life. However, Martin dismissed these claims by pointing out to Eddie the incredible coincidence of him and his distant grandson existing in the same moment in time and that he is the only person in that era who Eobard is incapable of killing. Martin believed that Eddie is the only individual in this entire scenario he exhibits free-will. Just as encouraged Eddie to stay, Martin noticed that one of the possible outcomes of opening up the wormhole would be the creation of a singularity, a black-hole capable of swallowing the entire planet and he immediately warns the rest of the team.
When The Flash ran to stabilise the singularity, Martin merged with Ronnie and flew up to the singularity in order to separate it in the eye. They succeeded in stopping the singularity from swallowing up Central city with some consequences. During their effort to destroy the singularity Ronnie and Martin separated and Ronnie was pulled into the singularity which killed him.
Six months after Ronnie's death, Martin became the new mentor of Team Flash. After meeting and speaking to Jay Garrick, he discussed the implications of the multiverse including Earth One, Earth Two and Zoom.
He later helped save Patty Spivot and stop Eddie Slick/Sand Demon and questioned Cisco about his odd behavior. He then learned Cisco was a meta-human and persuaded him to use his abilities for the better and tell the team. Stein began talking to the team when he fainted which was found to be the effect of not being merged with his second half for a long period of time.
A few hours later, he recovered from his state and helped to stop Lewis Snart and Leonard Snart/Capitain Cold from stealing the diamonds. He also contributed in helping Lisa Snart. Stein immediately starts bursting into blue flames before falling on the floor unconscious.
The team discovered he needed someone else to merge with Stein in order for him to stay alive. The only two possible matches were Jax Jackson and Henry Hewitt. Henry Hewitt was not able to merge with Stein as he was incompatible so they had to resort to the second choice Jax Jackson. During a fit of rage Henry discovered his new abilities. Henry was both enraged and jealous of this decision and tried attacking Caitlin in the garage Jax was working in, Jax successfully defended her and they both escaped to S.T.A.R. Labs. The team found out Henry was wreaking havoc in the stadium Jax used to play in. After discussing the dangers of Henry the team decided in order to tackle Henry, Jax Jackson and Martin Stein had to merge. The merge was successful and Jax had the physical and mental control of firestorm. After a long battle with Henry Hewitt, Firestorm and The Flash succeeded in defeating Henry. Later Jax Jackson and Martin Stein decided to leave Central City in order to train.
Aiding Rip Hunter
In January 2016, Jefferson Jackson and Stein were still in Pittsburgh, where they were up against a criminal at a chemical plant as Firestorm. Stein told Jax to be careful, as 83% of the chemicals were flammable. Jax however still shot fireballs all over the place. While Firestorm defeated the man, Stein was still upset that Jax doesn't listen to him. Jax told him to stop treating him like one of his "snot nosed undergrads" when they were intercepted by Rip Hunter. He lost opportunity to meet his future wife Clarissa, after meeting with "sexy assassin from the future" Sara Lance, and her proceeding to knock him out and he refused to go to a Facility Mixer. Rip Hunter convinced the young Martin Stein to go and meet his dear Clarissa. Stein became depressed upon realizing that despite believing he had matured over the years, he was still just as arrogant as his younger self. Jax helped encourage Stein by showing him that he has indeed matured into a kind, smart and selfless man who is willing to do anything to save the world to make it a better place.
Martin is a pacifist, having protested in the Vietnam War. He also hated pizza before merging with Ronnie. After merging he picked up some of Ronnie's characteristics, such as obsession with pizza. Martin is also shown to have a childish and laid back personality. One example was when he stated he was "game" if Ronnie was also willing to try to separate. He is also shown to have a sense of humor, telling Ronnie they should not fight on their wedding day shortly before officiating Caitlin and Ronnie's marriage. He also believed that any relationship should be prioritized above everything else.
On his first encounter, he is shown being cold towards Team Flash's camaraderie, asking if they were going to start chanting soon. However, after being rescued by the Flash, with the help of the team, he seems to have warmed up to the idea of the collaboration. This is even more apparent when he returns with Ronnie to help Barry. Not only does he help Barry travel back in time, he also helps a disheartened Eddie understand his role in everything that was happening.
Martin is very articulate and speaks in a very cultured and academic way that is sometimes misconstrued as arrogant or sometimes impossible to even understand; because of this, he is generally incapable of referring to someone by their nickname, calling Ronnie "Ronald" (despite "Ronnie" being his actual and legal name), calling Jax "Jefferson" and everyone else either Mr. or Ms. followed by their second name.
In combat and as Firestorm, Martin is very brave, dangerous, and sometimes brutal, despite his personality when not fighting. He attacked Barry and tried to kill him by dropping him from the sky, out of anger for Barry and his team not leaving him alone as he told them to. Even without Firestorm, he was brave enough to fight hand to hand with Time Pirates and knock out some of them on his own. While co piloting Firestorm's body, he was willing to be part of killing in battle. In this regard, while he dislikes fighting, he is not afraid of it and will fight as a last resort or to defend himself.
Powers and abilities
- Firestorm Matrix: When Jax merges with Professor Stein, the two create the nuclear-powered composite being Firestorm. The F.I.R.E.S.T.O.R.M. Matrix are controlled by two individuals, or “halves”; when they achieve physical contact, the Matrix takes over their biology and merges them into a singular being. When the two halves of Firestorm merge, the Matrix has them take on the form of the individual that has the stronger body.
- Psychic link: Jefferson can hear Martin Stein's disembodied voice while the two of them are merged into Firestorm. Even when they are separated, their link allows them limited communication of sensations or emotions. This link can be so strong that if Stein wanted to prevent whoever he merged with from attacking, he can restrain the nuclear energy from being shot out.
- Nucleokinesis: Firestorm is virtually a living reactor, and as such, creates great amounts of nuclear energy via the in numerous atomic reactions constantly occurring in his body. That and his mental capacity to process both fission and fusion, allow him to harness the energy emitting from his either his own body or any near source of energy that’s near.
- Pyrokinesis: Due to the nuclear nature of the transmutation of the two bodies, Firestorm is able to produce nuclear energy in the form of fire from parts of his body. He can use his control over the energy to project it willingly in the form of concussive blasts. These “nuclear blasts” are often shown to be quite powerful and have shown to be able to knock unarmed humans out unconscious and are hot enough to burn through solid structures and even cause harm to meta-humans.
- Flight: Firestorm has so far seen to have at least two methods to achieve flight. The first and most common is when he uses fires nuclear blasts downward at a consistent rate, thereby defying generating enough force to defy gravity and allow for stable profusion and gliding. This flight style is his preferred and most practiced choice. The second method is unclear, as he is shown to be able to fly at impressive speeds without the need of his blasts. How he achieved this skill or how he even does it is unclear.
- Nuclear absorption: Firestorm has shown the ability to not only generate nuclear power, but also contain the energy coming from outside sources by absorbing its output. He did so when he absorbed the blast from Vandal Savage’s nuclear warhead. As shown by Martin, while separated, he is still able to passively absorb energy, albeit on a smaller scale and with a greater strain.
- Hand-to-Hand combatant: Martin has proven himself to be a skilled fighter to an unknown degree. This is evidenced when he managed to fight, defeat, and disarm an armed time pirate.
- Skilled in using Morse code: Martin is familiar enough and able to construct Morse code messages without having to look it up.
- Genius-level intellect: From a young age, Martin showed exceptional intellect as skipped from 10th grade all the way to college and by age 25, he had two PhDs as well as nearing a third, plus was a leading expert in a field of study. Martin's profound knowledge of the quantum physics is shown by the many awards he won; not only is he good at theorizing, his project, F.I.R.E.S.T.O.R.M., has put into practice that which has yet to be successfully done by mankind. He is also especially interested in the concept of time travel and has several ideas on this topic alone.
- Indomitable will/Tolerance for pain: After getting captured by General Eiling, he was tortured in order to get the secrets of Firestorm, so they could weaponize it. However he resisted (something even Eiling was surprised by) without saying a word. He endured a similar treatment when he was captured by Valentina Vostok and Vandal Savage in 1986, only giving in when they threatened Ray Palmer and Mick Rory rather than himself
- Rabbinical knowledge: Having attended a seminary or a Jewish theological college, Martin has become a fully legitimate Rabbi, and as such, he is able to read in Hebrew and is licensed to pronounce marriage.
- Bilingual: Martin is capable of fluently speaking English and Hebrew.
- Sharpened mind: When they first successfully fused into Firestorm, Martin was able to detect enemy presence behind them before Ronnie.
- Ionized radiation: The Firestorm Matrix can be destabilized by bombarding its cellular structure with ionized radiation, temporarily disabling Firestorm's powers. Though it will not separate Ronnie and Martin it will cancel Firestorm's powers for a small amount of time.
- Prolonged separation: In the six months since Ronnie's death, Martin discovers that prolonged separation from his other half will kill him, unless another meta-human who can merge with him is found.
- Lost of thought: He occasionally gets side-tracked and loses focus on the current topic.
- Mild forgetfulness: Due to his constant lost of thought, he loses his keys constantly.
- Limited control: As Firestorm, Martin has very little control what the Firestorm will do, unless he has the superior body of the two. If the host will have superior body to Stein and is in control, Stein has to count that they will separate or he will be stuck in that particular body as long as the host wants to. However, when Valentina, a mad Russian scientist who wanted to become Firestorm herself, had merged with Stein and was attacking everyone, and was even about to attack Jefferson, Stein was able to restrain her from launching a blast.
- Power cane (Formerly): During the search for a new host for the FIRESTORM Matrix, Cisco created a cane using parts from Eobard Thawne's wheelchair to stabilize his condition. However over time, the device became useless.
DC's Legends of Tomorrow
Behind the scenes
- In the DC comics, Dr. Martin Stein became one half of the nuclear superhero Firestorm when he was combined with Ronnie Raymond after an explosion at a nuclear facility. Similar to how the Flash tapped in to the Speed Force for his powers, Firestorm used the Firestorm Matrix to transmute elements.