All-American Comics #19
Showcase #34 (Oct. 1961)
Suicide Squad #44 (August 1990)
Atom One Million:
DC One Million 80-Page Giant #1,000,000 (August 1999)
DCU: Brave New World (2006)
Bill O'Connor (writer)
Ben Flinton (artist)
Julius Schwartz (editor and co-plotter)
Gardner Fox (writer)
Gil Kane (artist)
Atom One Million:
|Alter ego||Al Pratt|
Justice Society of America
Black Lantern Corps
Black Lantern Corps
Atom One Million:
Justice Legion Alpha
(Ray, Cray, & Ryan):
The Atom is a name shared by five superheroes appearing in American comic books published by DC Comics.
The original Golden Age Atom, Al Pratt, was created by writer Bill O'Connor and artist Ben Flinton and first appeared in All-American Publications' All-American Comics #19 (October 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. Another Atom from the 853rd Century first appeared as part of Justice Legion Alpha in August 1999.
The Atom has been the star of multiple solo series, and four of the five have appeared as members of various superhero teams, such as the Justice Society of America, the Justice League, the Suicide Squad, and the Justice Legion Alpha.
Main article: Atom (Al Pratt)
The original Atom, Al Pratt, first appeared in All-American Comics #19 (October 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.
Main article: Atom (Ray Palmer)
The Atom introduced during the Silver Age of comic books in Showcase #34 (1961) is physicist and university professor Raymond Palmer, Ph.D. (He was named for real-life science fiction writer Raymond A. Palmer, who was himself quite short.) After stumbling onto a mass of white dwarf star matter that had fallen to Earth, he fashioned a lens which allowed him to shrink down to subatomic size. Originally, his size and molecular density abilities derived from the white dwarf star material of his costume, controlled by mechanisms in his belt, and later by controls in the palms of his gloves. Much later, he gained the innate equivalent powers within his own body. After the events of Identity Crisis, Ray shrank himself to microscopic size and disappeared. Finding him became a major theme of the Countdown year-long series and crossover event.
Prior to Ray Palmer's trip to the Amazon Jungle, he learns his wife Jean Loring has had an affair with her colleague, Paul Hoben. Palmer and Loring got a divorce. Later, Palmer offers his blessing to the couple when they marry, and he offers Hoben his size-changing belt so that Hoben can protect Ivy Town after Ray returns to the Morlaidhans. Adam Cray would later steal this belt; Hoben never uses the costume or name of the Atom.
Adam Cray, son of the murdered Senator Joseph Cray, first appeared as the Atom in the pages of Suicide Squad #44 by John Ostrander (August 1990). Cray was initially believed to be Ray Palmer in disguise by members of the team. Cray had been recruited by Palmer (who faked his own death) to apprehend the Micro Squad, a group of villains that had been reduced in size. Palmer intended to use Cray to uncover a shadowy government cabal which was using Palmer to discover the secret identities of other costumed heroes (Palmer's own identity no longer being secret). While Palmer infiltrated the Micro Squad, Cray would attract 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 remained with the Suicide Squad briefly, serving as a secret weapon whose existence was unknown to others of the Squad. Cray saves Amanda Waller from a group of assassins. At one point, Cray approaches Deadshot about his role in Senator Cray's murder. Later, Cray is impaled through the chest with a screw by Blacksnake, a Micro Squad member who believes him to be Palmer.
After the unanticipated murder of Cray, 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.
During the events of Blackest Night, Adam's corpse is reanimated as a member of the Black Lantern Corps alongside several other fallen Suicide Squad members. Following his reanimation, Adam and the other Black Lanterns travel to Belle Reve and attack Bane and Black Alice. Adam is apparently destroyed by the Manhunter's self-destruct mechanism, unleashing an explosion of Green Lantern energy that eradicates the Black Lanterns.
In DC Rebirth, Adam Cray is the son of Senator Cray and Ryan Choi's roommate at Ivy University. Senator Cray also attended Ivy and expected Adam to attend Ivy as well. He first meets Ryan when he walks into their dorm with heavy luggage and kindly introduces himself. Adam teaches Ryan how to play rugby and video games.
Main article: Atom (Ryan Choi)
Ryan Choi, as described by DC solicitations, is "a young hotshot professor who's filling the extra spot on Ivy University's teaching staff. .. and who inadvertently ends up filling the old Atom's super-heroic shoes". This new Atom is based on a redesign by Grant Morrison. He debuted in the Brave New World one-shot, a preview of projects, and then appeared in the series The All-New Atom, written by Gail Simone. He is later murdered by Deathstroke and his Titans.
In September 2011, The New 52 rebooted DC's continuity. In this new timeline, a new, female Atom is introduced, Rhonda Piñeda, a Hispanic American college student from Ivy Town. She is revealed to be working as a reluctant spy for Amanda Waller and Steve Trevor, gathering intel on the new Justice League recruits. She is noted to be "the most important member of the Justice League of America" by Steve Trevor. At the conclusion of the "Trinity War" storyline, she is revealed to in fact be betraying both teams; she hails from the alternate universe of Earth-3, where she is a member of the Crime Syndicate operating under the name Atomica. She also reveals that by placing a sliver of Green Kryptonite in Superman's optic nerve, she caused him to accidentally kill Doctor Light, with the added effect of severely weakening and almost killing Superman over time.
Atomica originally worked on Earth-3 with Johnny Quick as a thief and killer. One night after killing two cops, they are cornered on the roof of S.T.A.R. Labs during a storm. Lightning hits a satellite, electrocuting Johnny and granting him speed powers. Rhonda falls inside the building and lands near Ray Palmer's Atomico work, gaining size- and density-changing powers. During the final battle with the Crime Syndicate, Atomica reduces her size and is killed when Lex Luthor steps on her.
Following the reboot of the multiverse after Dark Nights: Death Metal, a new Earth-3 and Atomica are created. Atomica is the lover of speedster serial killer Johnny Quick and accompanies him on his high-speed murder spree across Central City.
An unnamed scientist in the 853rd Century performed experiments in superstring theory that creates a singularity and whose radiation alters his physical make-up. When the singularity threatened to expand and destroy his universe, he enters it in an attempt to save the universe but instead finds himself on an interdimensional bridge to another universe as his own is wiped out, unable to stop it. At the end of the bridge, he finds Superman Prime who came to help but was too late. Stranded, he searches this universe for remnants of the one he lost, in time taking the name the Atom and joining the Justice Legion Alpha when he helped them defeat the Bizarro-Legion. This Atom's powers differ from his predecessors in that he doesn't shrink but breaks up into several smaller duplicates of himself divided amongst his mass. At atomic size, these duplicates can mimic elements such as gold and oxygen. 
Each of the versions of Atom have their own enemies:
Frank Miller portrayed Ray Palmer as a major player in Batman: The Dark Knight Strikes Again as part of Batman's resistance. 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. in Dark Knight III, He was then instrumental in the liberation of Kandor until killed by their leader, Baal. 
Main article: Tangent Comics
In the Tangent Comics imprint, the Atom is "Arthur Harrison Thompson", a subject of radiation testing on human beings. The first hero in the Tangent timeline, he inadvertently caused the Cuban Missile Crisis to escalate into a limited nuclear exchange that obliterated Florida and Cuba in 1962, unknown to his fellow Americans. Thompson was succeeded by his son, who was killed by the Tangent Comics version of the Fatal Five, and a grandson named Adam, who, in Tangent: Superman's Reign, is being held captive by Superman.
It is suggested in the Tangent series that the Atom's name was at least in part chosen because of the abbreviation of his full name "Arthur Harrison Thompson" on his barracks door to simply "A. Thom."
Also in the Tangent series, the Atom's presence as America's first superhero during the 1960s has led to a huge cultural impact, and in this world many significant points in pop culture have been effected by his presence; for instance The Beatles choose to be called "The Atomiks", further more TV shows such as The Beverly Hillbillies became The Superman Hillbillies, The Dick Van Dyke Show became The Dick Van Hero Show and Get Smart became Get Powers.
Main article: Elseworlds
In the final issue of 52, a new Multiverse is revealed, originally consisting of 52 identical realities. Among the parallel realities shown is one designated "Earth-2". As a result of Mister Mind "eating" aspects of this reality, it takes on visual aspects similar to the pre-Crisis Earth-2, including the Atom among other Justice Society of America characters. The names of the characters and the team are not mentioned in the panel in which they appear, but the Atom is visually similar to the Al Pratt Atom. Based on comments by Grant Morrison, this alternate universe is not the pre-Crisis Earth-2.
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. On the newly introduced Earth-52, Atomarsupial is one of the metasimian Primate Legion 
|The Atom Archives, Vol. 1||Showcase #34-36, The Atom #1-5||208||1-56389-717-2|
|The Atom Archives, Vol. 2||The Atom #6-13||208||1-4012-0014-1|
|Sword of the Atom||Sword of the Atom #1-4 and Sword of the Atom Special #1-3||232||1-4012-1553-X|
|DC Comics Presents: The Atom||Legends of the DC Universe #28-29 and 40-41||96|
|My Life in Miniature||The All-New Atom #1-6, Brave New World #1||160||1-4012-1325-1|
|Future/Past||The All-New Atom #7-11||128||1-4012-1568-8|
|The Hunt for Ray Palmer||The All-New Atom #12-16||128||978-1-4012-1782-2|
|Small Wonder||The All-New Atom #17-18 and 20-25||192||978-1-4012-1996-3|