The Hadean Eon is the earliest geological eon in Earth's history, spanning from about 4.6 billion to 4 billion years ago. It began with the formation of the Earth and is characterized by extreme volcanic activity, a molten surface, and the gradual cooling that allowed the formation of a solid crust. The name "Hadean" comes from Hades, the Greek god of the underworld, reflecting the harsh conditions of this time. During the Hadean Eon, the atmosphere was primarily composed of gases like carbon dioxide and water vapor, with little to no oxygen. This eon set the stage for the development of the Earth's first oceans and the eventual emergence of life in later eons. The Hadean is crucial for understanding the planet's early environment and the processes that shaped its formation.