Microspace

Microspace is an alternate universe from the IDW portion of the Generation 1 continuity family

The subatomic realm of Microspace was created by Micronus Prime, and is home to the swashbuckling Micronauts. The gigantic body of their universe's creator still lies at the very center of their universe, containing an interdimensional gate that allows intrepid inhabitants of this tiny universe to travel to and from our reality.

It is also referred to as Micronus Space, and may be related to subatomic inner space.