Earth is the third planet from the Sun. It is also the planet we inhabit. The Earth is made up of several layers, the most prominent among them being the crust, the mantle, and the core. The core is made up of two layers, the inner core and the outer core. Between the crust and the mantel is the Mohorovic discontinuity, or Moho zone. The Earth hosts all known life forms within our current range of knowledge.