Precambrian time covers the vast bulk of the Earth's history ... is not unlike one of the first life forms that appeared in the Precambrian era. Photograph by Joel Sartore, National Geographic ...

The Precambrian encompasses 86 percent of the history of Earth. As its name implies, this includes all of geological time prior to the Cambrian period. Hadean Era (4,550-3,850 mya) The Precambrian ...