The Proterozoic () is a geological eon representing the time just before the proliferation of complex life on Earth. The name Proterozoic comes from Greek and means "earlier life",the Greek root protero-,means "former, earlier" and zoic-,means "animal, living being". The Proterozoic Eon extended from to (million years ago), and is the most recent part of the Precambrian. It is subdivided into three geologic eras (from oldest to youngest): the Paleoproterozoic, Mesoproterozoic, and Neoproterozoic.