Archaeozoic era is considered as the age of

The Archaeozoic (Archean) eon, spanning from about 4 to 2.5 billion years ago, is characterized by the emergence of the simplest life forms on Earth - primarily single-celled organisms like protists and prokaryotes. Complex multicellular organisms like fishes and amphibians appeared much later in the Proterozoic and Phanerozoic eons.