Deep inside each of the billions of Brahmanda egg shaped universes coming from the Body of Maha Vishnu, is a secondary universe where unlimited Garbhodakashayi Vishnus resides. From His naval, a stem has grown with a lotus flow at its end, this is where Lord Brahma resides and builds his material universe and all the Planetary Systems also located deep within each Brahmanda (Our inner universe has 14 planetary systems) Each surrounding Brahmanda is different in size, this is based on how many heads each Lord Brahma has, some have 4 or 40, or 400 even 1000 or 10,000. Therefore all Brahmanda's range in different sizes.

Here we see in this painting below what is deep within each of the millions of Brahmanda egg shaped universes coming from the Body of Maha Vishnu.

As shown in painting, deep inside each Brahmanda is a secondary Universe where Garbhodakashayi Vishnu resides and from His naval a stem has grown with a lotus flow at its end where Lord Brahma resides.

In this inner universe deep within the surrounding Brahmanda, Brahma builds and creates 14 different Planetary Systems that all exist within the lotus stem growing from Garbhodakashayi Vishnu's naval.

In our Brahmanda, the small inner material universe is called Bhu-Mandala and is 4 billion miles in diameter according to Srimad Bhagavatam's 5th Canto.

It is important to understand that each material universe, like our Bhu-Mandala Universe with its 14 different Planetary Systems, are actually encased and surrounded by a greater Universal body called a Brahmanda.

The size of our outer surrounding Brahmanda covering of our small material universe within, made up of 7 massive material layers, are collectively 44 quadrillion 444 trillion 444 billion miles in diameter as seen in the below painting.

The painting does not reveal the real size of our 4 billion mile diameter Bhu-Mandala Universe that is deep inside its massive surrounding Brahmanda.

If it did, you would not even see our smaller inner material Universe because the Brahmanda is so massive.