So there is no sex there. Because we have no experience with spiritual energy, we think that Brahmā’s birth from the navel of Viṣṇu is simply a fictional story. We are not aware that spiritual energy is so powerful that it can do anything and everything. Material energy is dependent on certain laws, but spiritual energy is fully independent.
Countless universes reside like seeds within the skin pores of Mahā-Viṣṇu, and when He exhales, they are all manifested. In the material world we have no experience of such a thing, but we do experience a perverted reflection in the phenomenon of perspiration. We cannot imagine, however, the duration of one breath of Mahā-Viṣṇu, for within one breath all the universes are created and annihilated. This is stated in the Brahma-saṁhitā. Lord Brahmā lives only for the duration of one breath, and according to our time scale 4,320,000,000 years constitute only twelve hours for Brahmā, and Brahmā lives one hundred of his years.