1. Big Bang: The beginning of the universe, marking the start of space, time, and all matter.

2. Formation of Galaxies: After the Big Bang, matter started to clump together due to gravity, eventually forming galaxies, including our own, the Milky Way.

3. Formation of the Sun: Within a galaxy, clouds of gas and dust collapsed under gravity to form stars, including our Sun.

4. Formation of Earth: The leftover material from the Sun's formation formed planets, including Earth.

So the complete sequence is: Big Bang → Galaxies → Sun → Earth.