This eon, which began about 541 million years ago, is characterized by the diversification and evolution of macroscopic organisms, including plants, animals, and fungi. The term "Phanerozoic" itself comes from the Greek words "phaneros" (visible) and "zoe" (life).

While life likely existed before the Phanerozoic, it was predominantly microscopic and left very little fossil evidence. The Phanerozoic Eon is when life became significantly more complex and diverse, leaving a rich fossil record that we can study today.