Chemically, the Earth can be divided into three layers: the crust (which is solid), the mantle (which can be divided into the upper and lower mantle and is solid/plastic), and the core (which can be divided into the outer core which is liquid, and the inner core, which is solid).
Did you know? Scientists determine the composition of the Earth through seismic monitoring (measuring earthquake waves) as well as measurements of gravitational and magnetic fields of the Earth.