The PreCambrian Time

This is a picture of the Hadean Eon

Hadean Eon
The Hadean Eon started about 4.5 billion years ago to 3.8 billion years ago. The Hadean Time is the earliest time in the PreCambrian Time. No rocks of this age are known on Earth, with the exception of a few meteorites.

Archaean Eon
It was between 3.8 and 2.5 billion years ago. Life began on Earth during the early Archaean, as indicated by the appearance of fossils in rocks about 3.5 billion years old. Archaen means "ancient."

Proterozoic Eon
The final era of the Precambrian, beginning 2.5 billion and ending 553 million years ago. Fossils of both singled celled life forms and more complicated life forms have been found in fossils from this time. Proterozoic means "early life."