To protect the Microuniverse from Psycho-Man and his minions.
|First appearance||Marvel Universe Avenger Earth Mightiest Heroes #6|
They Came From Inner Space
When Psycho-Man learned of the Macrouniverse (Earth), he sent his army to conquer Earth and to eliminate Hank Pym (who created a bridge between the two universes), the Microns were his army, finding to the Wasp, a member of the Avengers who was fighting with Psycho-Man's army.
When Janet discovered their objectives, she helped them fight against the army of Psycho-Man, and used Pym Particle capsules to shrink and release Iron Man and Captain America, who had been captured by Psycho-Man's henchmen, leading to a battle between the two groups, however, the Avengers and the Microns were surrounded by the army, until Wasp changed to normal size and returned the Microns to their own world, taking the army, and continue fighting against Psycho-Man.