ALL Brahmanda universes that originate from Maha Vishnu, have a secondary inner smaller universe deep inside of them that houses Garbhodakashayi Vishnu, Lord Brahma and the different Planetary Systems.

Lord Krishna in Goloka Vrindavana, also expands as all the Narayana and Vishnu Forms in the perpetual youthful Vaikuntha Planets.

Krishna then eventually expands as Maha Vishnu (Karanodakshayi Vishnu) to manage and provide material facilities (including all material bodily vessels) in this temporary decaying material creation.

It is through Maha Vishnu's dreaming, that He creates all the massive material universal shells known as Brahmandas.

He then provides all material bodily vessels to each marginal living entity that enters the material creation.

In this way, all jiva souls who have chosen to enter the material creation, get all their material bodily facilities originally from Maha Vishnu that are later further managed by Garbhodakashayi Vishnu.

This happens when Maha Vishnu expands Himself into a secondary universe deep in each Brahmanda as Garbhodakashayi Vishnu.

This smaller secondary universe is encased and surrounded by the outer Brahmanda.

And from Garbhodakashayi Vishnu, Lord Brahma appears in each of inner universes and builds the many Planetary Systems.

The size of all the Planetary Systems vary within each universe, that exists in the center of each Brahmanda.

In our small universe within our Brahmanda, we have 14 Planetary Systems.

Other universes inside their Brahmanda, may have many more Planetary Systems.

So it is important to understand that deep inside each Brahmanda universal shell, a secondary smaller universe exists at its center.

Furthermore, the size of each Brahmanda and their inner universe within it, depends on the how many heads their Lord Brahma has.

Some Lord Brahmas, like ours, has only 4 heads, while other Brahma's within their universe inside their Brahmanda, may have 10, 20, 50, 500, 1000, 100,000 or even a million or more heads.

In this way, all the billions of Brahmanda universes coming from the Body of the sleeping Maha Vishnu (as seen in painting below)

ALL Brahmandas have a secondary inner universe deep inside them that houses Garbhodakashayi Vishnu, Lord Brahma and the different Planetary Systems.