The Atom is a name shared by several fictional comic book superheroes from the DC Comics universe.
There have been four characters who have shared the Atom codename. The original Golden Age Atom, Al Pratt, was created by Ben Flinton and Bill O'Connor and first appeared in All-American Publications' All-American Comics #19 (Oct. 1940). The second Atom was the Silver Age Atom, Ray Palmer, who first appeared in 1961. The third Atom, Adam Cray, was a minor character present in Suicide Squad stories. The fourth Atom, Ryan Choi, debuted in a new Atom series in August 2006.
The Atom has been the star of multiple solo series, and three of the four have appeared as members of various superhero teams, such as the Justice Society of America, the Justice League, and the Suicide Squad.
The original Atom, Al Pratt, first appeared in All-American Comics #19 (Oct. 1940). He initially had no superpowers; instead, he was a diminutive college student and later a physicist who was depicted as a tough guy, a symbol of all the short kids who could still make a difference. Pratt was a founding member of the Justice Society of America, later gaining limited super-strength, and an energy charged 'atomic punch'. He died in the charge against Extant during the Zero Hour.
Adam Cray, son of the murdered Senator Cray, first appeared as the Atom in the pages of Suicide Squad #44 by John Ostrander (August 1990). At first Cray was widely believed to be Ray Palmer in disguise (by both the fans and the characters). Actually Cray had been recruited by Palmer himself, who faked his death, in order to apprehend the Micro Squad (a group of villains that had been shrunk down) as well as uncover information about a shadowy government cabal, who were interested in Palmer's knowledge of the other heroes' secret identities (his own identity being no longer a secret).
While Palmer would infiltrate the Micro Squad, Cray would gather the attention of the Cabal as the new Atom, so that no one would notice Palmer assuming the identity of a fallen Micro Squad member.
Adam Cray ran with the Suicide Squad only for a short while, serving as a secret weapon most of the time, and his existence was for a while even unknown to others of the Squad. Cray even saves a wounded Amanda Waller from a group of assassins. At one point, Cray approaches Deadshot about the fact that Deadshot had murdered his father. Deadshot tells Cray that he would get one free shot at him. Soon after, on a mission, Cray is impaled through the chest by Blacksnake, a Micro Squad member who believes him to be Palmer.
After the murder of Cray (a move Palmer had not foreseen), Palmer reveals himself and defeats Cray's murderer. The ruse ended, Palmer explains himself to the Justice League, who had been searching for him, after hearing rumors of a new Atom.
Born in Hong Kong, Ryan was a longtime protege 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 very fabric of reality to warp in Ivy Town's vicinity, making it a nexus of paranormal activity. Many parties, including the ancient "Cancer God" M'Nagalah and the microscopic aliens known as "The Waiting," consider Ryan a key player in the war and have made attempts to recruit, capture, or kill him.
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 Choi was involved in the search for the missing Ray Palmer, travelling 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.
Frank Miller portrayed Ray Palmer as a major player in Batman: The Dark Knight Strikes Again. He was taken prisoner by Lex Luthor and made to live in one of his own petri dishes for a period of months until his rescue by Catgirl. He was then instrumental in the liberation of Kandor.
In Countdown #30, the Challengers from Beyond encountered Earth-15, a world where the sidekicks had taken their mentor's places. On this Earth, the Atom is Jessica Palmer, a genius who graduated from MIT at age eight. The Search for Ray Palmer - Red Son features the Ray Palmer of Earth-30, an American captured by the Superman of a communist Russia. Countdown: Arena also depicts the Ray Palmer of Earth-6, who through unknown circumstances now has the powers and title of the Ray. The Search For Ray Palmer: Superwoman/Batwoman briefly features a female version of The Atom.