#Multiverse

The multiverse (or meta-universe) is a hypothetical set of various possible universes including the universe which humans live in. Together, these universes comprise everything that exists: the entirety of space, time, matter, energy, the physical laws and the constants that describe them. The miscellaneous distinct universes within the multiverse are called the "parallel universes", "other universes" or "alternative universes".

The concept of multiverses is mentioned many times in Hindu Puranic  literature, such as in the Bhagavata Purana;

Every universe is covered by seven layers — earth, water, fire, air, sky, the total energy and false ego — each ten times greater than the previous one. There are innumerable universes besides this one, and although they are unlimitedly large, they move about like atoms in You. Therefore You are called unlimited (Bhagavata Purana 6.16.37)

Analogies to describe multiple universes also exist in the Puranic literature:

Because You are unlimited, neither the lords of heaven nor even You Yourself can ever reach the end of Your glories. The countless universes, each enveloped in its shell, are compelled by the wheel of time to wander within You, like particles of dust blowing about in the sky. The śrutis, following their method of eliminating everything separate from the Supreme, become successful by revealing You as their final conclusion (Bhagavata Purana 10.87.41).

The layers or elements covering the universes are each ten times thicker than the one before, and all the universes clustered together appear like atoms in a huge combination (Bhagavata Purana 3.11.41)

And who will search through the wide infinities of space to count the universes side by side, each containing its Brahma, its Vishnu, its Shiva? Who can count the Indras in them all--those Indras side by side, who reign at once in all the innumerable worlds; those others who passed away before them; or even the Indras who succeed each other in any given line, ascending to godly kingship, one by one, and, one by one, passing away (Brahma Vaivarta Purana).