The formation of Earth began about 4.5 billion years ago from a cloud of gas and dust in space. This material, known as a solar nebula, collapsed under gravity, leading to the creation of the Sun and surrounding planets. As particles collided and stuck together, they formed larger bodies called planetesimals, which eventually merged to create Earth. During its early years, Earth was a molten mass due to intense heat from collisions and radioactive decay. As it cooled, a solid crust formed, and water vapor condensed to create oceans. This process set the stage for the development of an atmosphere and, eventually, life.