The Precambrian Eon is the longest stretch of time in Earth's history, constituting around 88 percent of the planet's total existence. It covers the period from the formation of Earth about 4.6 billion years ago until the beginning of the Phanerozoic Eon, approximately 541 million years ago. The Precambrian Eon is characterized by a remarkable transition from a barren and lifeless planet to one that gradually developed the conditions necessary to sustain complex life.