The Proterozoic Eon is a geological eon that spans approximately 2.5 billion to 541 million years ago. It is characterized by significant geological and biological changes, including the appearance of complex multicellular life forms, the rise of oxygen levels in the atmosphere, and the formation of supercontinents like Rodinia and Pannotia. The Proterozoic is divided into three distinct time periods: the Paleoproterozoic, Mesoproterozoic, and Neoproterozoic. Research in the Proterozoic Eon aims to understand the evolution of Earth's early life forms, the development of the atmosphere and climate, and the tectonic and geologic processes that shaped the planet during this time.