Planet Earth was created under the force of gravity, when stellar dust and rocky debris from the solar nebula combined. “Proto-Earth” was completely molten, its atmosphere toxic. A collision with planetoid Theia formed the Moon. Earth was pummeled by asteroids, clearing the way for the first microbial life forms. Oceans took shape and the Earth contained oxygen. Supercontinents split and merged, driving Earth into multiple ice ages and greenhouses. Algae and multicellular organisms developed, followed by the arrival of animals during the Cambrian Explosion. Massive global events guided extinctions, evolution and the arrival of land plants, mammals, dinosaurs and hominins. Earth’s history is so vast, it’s split into four eons, ten eras, twelve periods and seven epochs.