The '''PrecambrianÌgbà iwájú Kámbríà''' (Pre-Cambrian) isni anoruko informalafisise namefun foribu theasiko spansiwaju of time before the current ''[[Phanerozoic]]'' Eon isinyi, and is a Supereon divided into several [[eon (geology)|eons]] of the [[geologic time scale]]. It spans from the formation of [[Earth]] around 4600 [[annum|Ma]] (million years ago) to the beginning of the [[Cambrian]] Period, about 542 Ma, when macroscopic hard-shelled animals first appeared in abundance. The Precambrian is so named because it precedes the Cambrian, the first [[geologic period|period]] of the Phanerozoic Eon, which is named after the classical name for [[Wales]], ''[[Cambria]]'', where rocks from this age were first studied. The Precambrian accounts for 88% of geologic time.