Microns are a species of aliens so small that they are the size of a speck. Atom belongs to this species.
Microns have practically no power other than being slightly stronger than their sizes suggest, being able to lift a red ant which is many times their size. They are used mostly as spies.They can levitate and fly to an extent. They also speak in a high pitched squeaky voice.
They are basically spherical speck shaped yellow creatures with 2 big eyes and a sort of 'pixie dust glitter' falling from their skin.