Voice: John C. McGinley
First Appearance: The Return
Status: Justice League Member

Professor Ray Palmer created a device that allows him to alter his size and mass. Becoming the superhero, the Atom, Palmer can shrink down to microscopic levels. Palmer is also an expert in nanotechnology. The Atom later became a member of the expanded Justice League.

When the android Amazo was returning to Earth, the Atom was sent to work with Lex Luthor to find a chink in the android's armor. While the other heroes battled Amazo, Atom and Luthor were working on a laser cannon that would stop Amazo. Their attempts were unsuccessful. The Atom tried to stop Amazo, but was thrown down. He even shrunk down himself and Luthor to a subatomic level, but they were discovered by the android. However, Luthor was able to talk with Amazo and get him to stop by explaining his ultimate purpose.

During the Dark Heart situation, the Atom returned to help the League using his vast knowledge of nanotechnology. He was able to get inside the core of the Dark Heart and give it a heart attack, causing it and all its drones to die.

The Atom also aided the Justice League in their final battle against Darkseid and his Parademon forces.