The Big Bang Theory is a cosmological model that explains the origin and expansion of the universe. According to this theory:
1. The universe began as an extremely hot and dense singularity.
2. It rapidly expanded and cooled down, leading to the formation of subatomic particles.
3. These particles combined to form protons, neutrons, and electrons, eventually leading to the formation of hydrogen and helium atoms.
4. Over billions of years, these atoms gradually coalesced to form stars, galaxies, and the vast structures we observe in the universe today.