SB 3.8.15

This lotus flower is the universal virata form, or the gigantic form of the Lord in the material world. It becomes amalgamated in the Personality of Godhead Visnu, in His abdomen, at the time of dissolution, and it becomes manifest at the time of creation. This is due to Garbhodakasayi Visnu, who enters into each of the universes. In this form is the sum total of all the fruitive activities of the living entities conditioned by material nature, and the first of them, namely Brahma, or the controller of the universe, is generated from this lotus flower. This first-born living being, unlike all the others, has no material father, and thus he is called self-born or svayambhū. He goes to sleep with Narayana at the time of devastation, and when there is another creation, he is born in this way. From this description we have the conception of three-the gross virata form, the subtle Hiranyagarbha and the material creative force, Brahma.