The Phanerozoic eon is the current eon in Earth's geological history, beginning around 541 million years ago and continuing to the present. It is characterized by the abundance of fossil evidence and the emergence of complex life forms, including plants, animals, and fungi. This eon is divided into three major eras: Paleozoic, Mesozoic, and Cenozoic. During the Paleozoic era, life transitioned from simple marine organisms to diverse land plants and animals. The Mesozoic era is known as the age of dinosaurs, while the Cenozoic era marks the rise of mammals and birds, leading to the modern ecosystems we see today.