The time from 3,800 million years to 2,500 million years ago; earth's crust formed; unicellular organisms are earliest forms of life - Archean [US], Archean eon, Archean aeon, Archeozoic, Archaeozoic, Archaeozoic aeon, Archaean
Type of: aeon, eon
Part of: Precambrian, Precambrian aeon, Precambrian eon, Precambrian period