During the timeline of the era, several different events took place, eventually helping to shape the Earth as we know it today.

During the Proterozoic, the Earth had cooled considerably from the previous Hadean eon when the planet was covered by molten lava.

Near the end of the Proterozoic, ice sheets were growing towards the equator, and the entire planet was possibly engulfed under a thin layer of snow and ice.

The Proterozoic Eon extended from 2.5 billion to 541 million years ago and is often divided into the Paleoproterozoic (2.5 billion to 1.6 billion years ago), the Mesoproterozoic (1.6 billion to 1 billion years ago), and the Neoproterozoic (1 billion to 541 million years ago) eras.

Megascopic eukaryotes first appeared about 2.3 billion years ago and became widespread by about 1.8 billion years ago.

Eukaryotes employed a form of respiration and oxidative metabolism; they had a central nucleus that could split into separate sex cells, and so for the first time a mixed and variable genetic code could be passed to younger generations.

Earth’s early atmosphere contained only small amounts of free oxygen

The oxygen-rich atmosphere that evolved later, and upon which oxygen-breathing life now depends, was a result of the origin of photosynthesis.

During the Precambrian, vast numbers of single-celled algae and cyanobacteria living in the seas eventually released enough oxygen to transform the environment.