This universe, or the universal sky which we can visualize with its innumerable planets, is shaped just like an egg. As an egg is covered by a shell, the universe is also covered by various layers. The first layer is water, the next is fire, then air, then sky, and the ultimate holding crust is pradhāna. Within this egglike universe is the universal form of the Lord as the virāṭ-puruṣa. All the different planetary situations are parts of His body. This is already explained in the beginning of Śrīmad-Bhāgavatam, Second Canto. The planetary systems are considered to form different bodily parts of that universal form of the Lord. Persons who cannot directly engage in the worship of the transcendental form of the Lord are advised to think of and worship this universal form. The lowest planetary system, Pātāla, is considered to be the sole of the Supreme Lord, and the earth is considered to be the belly of the Lord. Brahmaloka, or the highest planetary system, where Brahmā lives, is considered to be the head of the Lord.