The Cenozoic era is that portion of time running from roughly 65 million years ago until just now. Sometimes the Cenozoic is called the "Age of Mammals", but what we generally mean by that is "Age after those pesky dinosaurs vanished", since there were mammals before the Cenozoic. Bats, whales, and mastodons are all Cenozoic inventions. Fish, birds, insects and flowering plants have also done well in the Cenozoic era. In fact, there were no flowering plants before the Cenozoic, much to the disappointment of dinosaur florists.

The Cenozoic era is divided by those who study such things into six epochs, which in turn combine into two periods:

The Paleocene epoch runs from 65 to 54 million years ago.

The Eocene epoch runs from 54 to 38 million years ago.

The Oligocene epoch runs from 38 to 23 million years ago.

The Miocene epoch runs from 23 to 5 million years ago.

The Pliocene epoch runs from 5 to 1.8 million years ago.

These five epochs together comprise the Tertiary period.

The Pleistocene epoch runs from 1.8 million years ago to now. The Quaternary period is made up of the Pleistocene epoch. If human beings weren't writing the rules, no one would find this last 1.8 million years to be very noteworthy. Some people define a Holocene epoch starting about 10,000 years ago, but most researchers seem to feel that this is a historical rather than a geological division.

Epochs in turn are divided into ages with names like Thanetian and Burdigalian, but we need not trouble ourselves with those tonguetwisters.

The Cenozoic era has been much cooler and drier than the preceding Mesozoic era. This is good for us, because it discouraged both the dinosaurs and the mildew from getting completely out of hand. On the other hand this coolness has led to a bunch of ice ages, and if one of those comes back we may find ourselves looking back fondly to Mesozoic days.

The inland sea that once covered most of North America vanished during the Cenozoic, which was good for Midwest USA real estate prices. The Cenozoic has also been a bang-up time for mountains: the Andes, Alps, Himalayas, Cascades and Rockies have all gotten much larger in this era.