The Microverse was a dimension that could be accessed by shrinking in the Marvel Universe. But, tied up in the Fantastic Four rights, when Marvel Studios put out the ANt-Man name, it was changed in title to "The Quantum Realm".
Well, waste not, want not. It appears that this week's DC Universe: Rebirth #1 out on Tuesday night/Wednesday, DC Comics is staking their claim with the Atom. Both of him.