Also generically known as Innerspace, Microverses are parallel dimemsions occurring within the fictional Marvel Universe. Microverses was often visited by the Fantastic Four in various adventures. A microverse could be defined as any universe which seems to be accessible only through vibrational attunement (shrinking). The former belief that these worlds actually exist within atoms may have given rise to the stock phrase "There are worlds within worlds". Actually, it is not these microverses that are microscopic in size but rather the nexuses making them accessible. Thus it is theoretically possible to enter the same microverse from different points on Earth. The volume of these microverses are contained in what is called a spacewall which can only be breached at certain points thus creating an accessible portal.

Worlds in microverses are often depicted as having planetary structures based on the highly popularized skeletal (ball and stick) molecular models. This is probably inaccurate due to new theories on the general appearance of atomic and subatomic particles. It is generally agreed that atoms and molecules themselves are not actually round solid objects but specifically structured electromagnetic vectors or clouds. The skeletal molecule look (especially with respect to the "junctions" connecting "planetary atoms") may be artificial and represent native technology, not natural planetary formations.

Although many microverses are assumed to exist, the most commonly visited microverse in the Marvel Universe is the one containing the regions known as Sub-Atomica and the Micronauts Homeworld. This Microverse was populated to a large extent by a group of refugee starfarers from a doomed planet, Ithaka. Led by their leader, known as Wayfinder, they eventually settled on Earth in ancient times only to be displaced again by demons. By the powers of Wayfinder's enchanted sword, they were relocated to the Microverse where they became ancestors of many of the races located there.

Other inhabitants of this Microverse include the Children of the Confluence of Stars and the Psycho-Man. A scientist exiled from Sub-Atomica, Psycho-Man was a re-curring enemy of the Fantastic Four. This Microverse is also the origin of the Enigma Force which regularly manifests itself on Earth in the form of Captain Universe.