Precambrian

The Precambrian is the vast span of Earth's history before multicellular life appeared, covering about 88% of the planet's existence. It includes the formation of Earth around 4.6 billion years ago, the development of its crust, oceans, and atmosphere, and the emergence of simple single-celled life forms like bacteria and algae. This era saw the buildup of oxygen in the atmosphere (the Great Oxygenation Event) and significant geological changes, but it lacks many recognizable fossils. The Precambrian ended roughly 541 million years ago, transitioning into the Cambrian period, when complex, diverse life began to flourish.