1. Giant Molecular Cloud: These clouds are vast and cold, containing mostly hydrogen and helium, along with traces of heavier elements.

2. Gravitational Collapse: A disturbance, such as a nearby supernova explosion, can trigger a collapse within the cloud. The densest parts of the cloud begin to pull in more material, creating a spinning disk of gas and dust.

3. Protoplanetary Disk: As the disk spins, it flattens and heats up. At the center, the material compresses and ignites, forming a protostar. Around the protostar, dust particles and gas clump together, forming planetesimals.

4. Planetesimal Accretion: Over millions of years, these planetesimals collide and stick together, growing larger and forming planets. This accretion process leads to the formation of the rocky inner planets and the gas giants further out.

So, the process of solar system formation starts with a giant molecular cloud, which then collapses under its own gravity. This leads to the formation of a protoplanetary disk, eventually leading to the birth of a star and the planets orbiting it.