Here's the hierarchy:

1. Eon: The largest unit of geologic time. Examples include the Phanerozoic Eon (the current one), the Proterozoic Eon, and the Archean Eon.

2. Era: An Eon is divided into Eras. Examples include the Paleozoic, Mesozoic, and Cenozoic Eras within the Phanerozoic Eon.

3. Period: An Era is divided into Periods. Examples include the Triassic, Jurassic, and Cretaceous Periods within the Mesozoic Era.

4. Epoch: A Period is divided into Epochs. Examples include the Paleocene, Eocene, and Oligocene Epochs within the Paleogene Period.

5. Age: The smallest unit of geologic time, used to further subdivide Epochs.

Let me know if you have any other questions about the geologic time scale!