The Earth is divided into four main layers - the crust, mantle, outer core, and inner core. The crust is the outermost layer and makes up only 1% of the Earth. Below the crust lies the mantle, which is the largest layer and consists of the upper and lower mantle. At the center are the inner and outer core, with the outer core being liquid iron that generates the Earth's magnetic field and the inner core being solid iron.