The Precambrian Era is divided into three eons, not two subdivisions. They are:

* Hadean Eon: This is the earliest eon, characterized by a very hot Earth and the formation of the first oceans.

* Archean Eon: This eon saw the rise of the first life forms, including single-celled organisms.

* Proterozoic Eon: This eon saw the diversification of life, including the first multicellular organisms and the evolution of eukaryotic cells.