What does the principle of uniformitarianism state

Explanation:

Uniformitarianism - "The Present is the Key to the Past"

Uniformitarianism is a geological doctrine. It states that current geologic processes, occurring at the same rates observed today, in the same manner, account for all of Earth's geological features. Thus, it assumes that geological processes are essentially unchanged today from those of the unobservable past, and that there have been no cataclysmic events in earth's history. As present processes are thought to explain all past events, the Uniformitarian slogan is, "the present is the key to the past.

The smallest unit of matter that has characteristic properties of it's element is an atom