When the Big Bang occurred and the universe was created, it was extremely hot, so much so that matter was still energy, and the four fundamental forces were still unified. Rapidly, the universe expanded, growing larger and larger as it cooled down for energy to coalesce in the form of fundamental particles and the four fundamental forces.
It began forming hydrogen and helium nuclei as the universe continued cooling.
Most people assumed that the universe was too hot and intense to support life, but the reality was that there was a phase in the universe's history where the temperature was within hospitable ranges. Where water would not have boiled if it existed.
It was known as the Habitable Epoch.
It was a phase in the universe's existence just ten million years long where temperatures were low enough to support chemistry, and the density of the universe was high enough for most matter to be spread across a relatively uniform cloud of hydrogen and helium.
