Eons are the largest division of geologic time, and they are subdivided into eras, periods, and epochs.

Here's a breakdown of the geologic time scale:

* Eon: The largest division of geologic time, spanning hundreds of millions to billions of years.

* Era: A subdivision of an eon, spanning tens to hundreds of millions of years.

* Period: A subdivision of an era, spanning millions of years.

* Epoch: A subdivision of a period, spanning hundreds of thousands to millions of years.

For example, the current eon is the Phanerozoic Eon, which is subdivided into the Paleozoic, Mesozoic, and Cenozoic eras.