Deep inside each massive Brahmanda material universe coming from Maha Vishnu, is a secondary smaller universe where Garbhodakashayi Vishnu, Lord Brahma and many planetary systems are found.

Inside each massive Brahmanda universe is a secondary smaller universe where Garbhodakashayi Vishnu and Lord Brahma reside.

In the painting below, we see millions of Brahmanda massive single almost spherical shaped material universes that each house a secondary smaller universe.

All these Brahmanda universes are coming from the Bodily pores and breathing of Maha Vishnu (also known as Karanadaksayi Vishnu)

So it is clearly explained above that deep inside each Brahmanda is a secondary smaller universe where Garbhodakashayi Vishnu and Lord Brahma reside.

Garbhodakashayi Vishnu and Lord Brahma's smaller universe is totally surrounded and encased in their particular Brahmanda, like a seed is surrounded by the outer shell layers of a Pine cone.

Also the outer Brahmanda is made up of seven material layers and surrounds each inner material universe deep inside of them.

This is inner material universe is where Garbhodakashayi Vishnu and Brahma reside, along with the many planetary systems.

In other words, Garbhodakashayi Vishnu and Brahma's inner smaller universe is encased in and surrounded by the outer massive Brahmanda universe that is made up of these 7 material layers.

These 7 material levels of material elements that make up the Brahmanda, are collectively 44 quadrillion 444 Trillion, 444 billion miles in diameter. 

However if the measurement is taken from the outer edge of the smaller inner material universe where Garbhodakashayi Vishnu and Brahma are, then the "full diameter" of the outer Brahmanda spherical universe is double that figure, which is 88 quadrillan, 888 trillion, 888 billion miles in diameter.

The inner material universes, that are found very deep within their Brahmanda, are very small in comparison to the outer massive Brahmanda surrounding it.

Some are just a mere 4 billion miles in diameter, like our single inner material universe according to the 5th Canto of Srimad Bhagavatam.

https://gauragopala.blogspot.com/2021/02/deep-inside-each-massive-brahmanda.html?m=1