Many Millennia is a term used to describe a very long period of time. It is often used to refer to a period of thousands or even millions of years. The term is made up of three parts: EON, EONS, and AEON. An EON is the longest division of geological time and is typically millions of years in length. EONS are a subdivision of an EON and are usually hundreds of millions of years in length. An AEON is the shortest division of geological time and is typically tens of millions of years in length. Together, these three terms can be used to describe a very long period of time, such as Many Millennia.