Born in
Hong Kong, Ryan Choi was a longtime protégé of
Ray Palmer who had been corresponding with him through letters. After Palmer's disappearance, Ryan moved to
Ivy Town in America to assume his mentor's place on the staff of Ivy University. Following clues left by Palmer, Ryan discovered a "bio-belt", allegedly the size and density-manipulating device used by his predecessor, and became the new Atom with Palmer's apparent blessing. Though taken with the superhero lifestyle, Ryan is a scientist first and foremost and approaches many of his adventures from the perspective of scientific discovery and investigation. Since taking his mentor's place, Ryan has found himself at the center of a conflict between the forces of science and magic. It has been claimed that the impossible feats performed by Ray Palmer during his superheroic career caused the fabric of reality to warp in Ivy Town's vicinity, making it a nexus of paranormal activity. As the Atom, Ryan has faced numerous challenges, including the shrinking serial killer
Dwarfstar, his strict and disapproving father, and being seduced, kidnapped, and even swallowed alive by the size-changing villainess,
Giganta. Through it all, his ingenuity and keen deductive mind have served him in good stead. Ryan is involved in the search for the missing Ray Palmer, traveling into the restored Multiverse along with
Donna Troy,
Jason Todd and a
Monitor nicknamed "Bob". Literally plucked back to New Earth, he leaves his role of dimension-hopper to
Kyle Rayner, returning to defend Ivy Town from a monster invasion. Later he is led to a mistaken belief that Ray Palmer has become an egocentric madman, and Ryan himself may be only a pawn of his mad fantasies. This is later revealed to be a ploy by Ray's old nemesis,
Chronos.
The All New Atom series ended with issue #25, when Ryan, with some help from the returned Ray Palmer, is able to discern between the truth and the lies fed by Chronos and his new assistant,
Lady Chronos, a former sweetheart of Ryan turned to crime. Ryan eventually discovers that Ray Palmer never knew of Choi: instead the bio-belt was a tainted gift from Jia, and the Ray Palmer letters a clever forging by Chronos, meant to force Ryan into accepting the Atom mantle, and taking the blame for the staging menaces sent against the city. However, due to Ryan's ability into sorting out the mess, besting the Chronos couple and restoring Ivy to normalcy, Ray finally gives him his blessing. Ryan expresses his desire to find a new identity for himself, since Ray, despite giving him his blessing earlier, had resumed using regularly his Atom identity. In
Justice League: Cry for Justice #1, Ray and Ryan are seen fighting
Killer Moth together, and at the end of the battle both of them show respect towards each other, with Ray asking Ryan to continue using the Atom name.
Brightest Day During the
Brightest Day event, Ryan is murdered by
Deathstroke and his new team of
Titans during their first mission. His corpse is then delivered in a matchbox to Dwarfstar, who is revealed to be the person who hired the Titans. His death caused some minor controversy, given both its timing and the supposed "lighter" new direction of DC Comics. A short time after Ryan's death, Deathstroke is briefly shown dismantling his bio-belt for an unknown purpose. In an interview done during
Comic-Con International 2010,
Titans writer Eric Wallace stated that Ryan's death would have major repercussions for the team, and would bring the Titans into conflict with the wider DCU. Ray Palmer eventually finds Dwarfstar in a hospital, where he confesses to hiring Deathstroke to kill Ryan. Armed with this knowledge, Palmer leaves to inform the Justice League, but not before telling Dwarfstar that Deathstroke will likely kill him for his betrayal. Ray seriously injures Deathstroke for killing his friend, but the Titans ultimately escape due to the intervention of
Isis and
Osiris. It is revealed that Deathstroke dismantled Ryan's bio-belt, intending to use its technology to heal his son
Jericho.
Convergence In the
Convergence crossover, when the alternate
Brainiac miniaturized the universe of the New Earth, Ryan appears to be alive and confronts Ray Palmer, who was battling the
Angor universe's Barracuda. Ryan reveals that after his death, his consciousness had survived in the universe where the Atoms' masses are shifted to whenever they change size. He later returns to the realm of the living after appropriating the flesh from Ray's severed hand to create a new body for himself. After Barracuda is defeated, the two Atoms work together to defeat Deathstroke, avenging Ryan's murder.
DC Rebirth Ryan makes his official debut in the new
DC Rebirth continuity as a teenage genius Ivy League college student tutored by Ray Palmer. Palmer reveals his identity as the Atom and enlists Ryan's help in fighting crime, talking to Ray from his lab in a tech support role. One day, after many adventures together, Ray goes missing. A week later, Ryan finds a message from Palmer along with one of his size-changing belts, asking the youth to come find him in the Microverse because he got stuck there when exploring a change in time and space. After receiving another scolding from Dean Plumm, Ryan heads back to the lab, using the bio-belt that Ray gave him to travel there through the Wi-Fi. When he arrives, he is met by Batman and Lobo who are there to recruit Ray Palmer into the new Justice League of America. Discovering that Ray is missing, Batman decides to leave until Lobo asks Ryan if he wrote down various equations to update the bio-belt on a blackboard. Impressed, Lobo decides that Batman should recruit Ryan, despite Batman not wanting to put him in danger. Lobo says it is Ryan's choice, and Ryan joins the JLA and sometime later, heads to Vanity, Oregon, to recruit the Ray into the team. In the 2025 series
Justice League: The Atom Project, Ray and Ryan work to reverse the aftermath of
Absolute Power, in which many heroes had their powers stolen by the
Amazo army. When the Amazos were destroyed, most of the heroes regained their powers, but some were unable to regain their powers, which were transferred to other heroes or civilians. ==Powers and abilities==