Precambrian Era

• The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale. It spans from the formation of Earth about 4570 Ma (million years) ago to the beginning of the Cambrian Period, about 541.0 ± 1.0 Ma, when macroscopic hard-shelled animals first appeared in abundance. The Precambrian is so named because it precedes the Cambrian, the first period of the Phanerozoic Eon, which is named after Cambria, the classical name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of geologic time.
• Not much is known about the Precambrian, despite its making up roughly seven-eighths of the Earth's history, and what little is known has largely been discovered in the past 50 years. The Precambrian fossil record is poor, and those fossils present (e.g. stromatolites) are of limited biostratigraphic use. This is because many Precambrian rocks are heavily metamorphosed, obscuring their origins, while others have either been destroyed by erosion, or remain deeply buried beneath Phanerozoic strata.
• It is thought that the Earth itself coalesced from material in orbit around the Sun roughly 4500 Ma (4.5 Ga) and may have been struck by a very large (Mars-sized) planetesimal shortly after it formed, splitting off material that came together to form the Moon (see Giant impact hypothesis). A stable crust was apparently in place by 4400 Ma, since zircon crystals from Western Australia have been dated at 4404 Ma.

Here's a short video about the Precambrian Era

http://www.youtube.com/watch?v=gvtsSejT-NI

Sources:

www.youtube.com
www.wikipedia.com