Current cosmological models maintain that 13.7 billion years ago, the entire mass of the universe was compressed into a singularity, from which it expanded to its current state (the Big Bang), the so-called cosmic egg.
The Hiranyagarbha Sukta announces: Hiranyagarbhah samavartatagre bhutasya jatah patireka asit, which means, Before creation existed the golden womb Hiranyagarbha, Lord of everything born. (Rig Veda 10.121.1)
The whole universe including sun, moon, planets, and galaxies was all inside the egg, and the egg was surrounded by ten qualities from outside. (Vayu Purana 4.74-75)
Furthermore the god Mithras is often depicted as appearing from within an egg.
In Hindu tantra, based on the Hindu philosophy of Kashmir Shaivism, the Shri Yantra represents the expansion of the universe from the cosmic egg after its creation by Shiva through the power of Shakti. The cosmic egg is represented by a dot in the center of the Shri Yantra mandala called the bindu.
The cosmic egg concept has caught the imagination of many science fiction and fantasy writers, including the creators of the Marvel Comics character Galactus. Galactus was the sole-survivor of the previous Big Crunch who, preserved in the cosmic egg, emerged as a being of immense power in the present universe. The cosmic egg concept was also used by DC Comics and Marvel comics in their Avengers/JLA crossover, in which it was used to capture their mutual enemy Krona.
Early 1990s Rotherham 3 piece band The Cosmic Egg were named for this concept, and many of their recordings featured imagery and lyrics inspired by the original Cosmic Egg concept.