The Proterozoic Eon was a period of geologic history from 2.5 billion years ago to about 542 million years ago and was the period between the Archean Eon and the Phanerozoic Eon. The Proterozoic Eon was divided into the Paleoproterozoic, Mesoproterozoic, and Neoproterozoic Eras, and during this eon, important events such as the Oxygen Catastrophe, possible worldwide glaciation, and the evolution of soft-bodied multi-cellular organisms.