How did galaxies begin to form 3 millions years or 300 million or 30 years after the Big Bang?

Galaxies began to form a few hundred million years after the Big Bang, around 400 million years later, as matter in the universe started to cool and coalesce under the influence of gravity. Initially, small fluctuations in the density of matter led to the formation of clumps, which attracted more gas and dark matter, eventually leading to the creation of the first stars. These stars grouped together to form proto-galaxies, which merged over time to create larger galaxies. The process continued as the universe expanded, allowing more complex structures to develop.