About 4.5 billion years ago, the Solar System began to form from a giant cloud of gas and dust. As this material collapsed under its own gravity, it created a spinning disk. In the center, the Sun formed, while particles in the outer regions began to stick together, forming larger bodies called planetesimals. Over time, these planetesimals collided and merged, eventually forming the Earth and other planets. The early Earth was a molten mass, but as it cooled, a solid crust formed. Water vapor condensed to create oceans, and the atmosphere began to develop, setting the stage for life.