The Priscoan aeon is a geological period that occurred roughly 4.5 to 4 billion years ago. During this time, the Earth was still in its infancy and the conditions were vastly different from what we see today. Synonyms for the Priscoan aeon include the Hadean eon, which is characterized by the formation of the Earth and early bombardment by asteroids. The Archaean eon follows the Hadean and is a period where life on Earth began to emerge. Other synonyms for the Priscoan aeon include the pre-Archean era and the pre-Cambrian era. Despite the many names associated with this early period in Earth's history, one thing remains certain: it was a time of great change and development.