1. Crust: The outermost layer of Earth, composed of relatively light, rigid rock. It's divided into oceanic crust (thinner and denser) and continental crust (thicker and less dense).

2. Mantle: The thickest layer, located beneath the crust. It's made of hot, dense rock that flows slowly over geological time. The mantle is responsible for plate tectonics.

3. Inner Core: The innermost layer of Earth, composed primarily of iron with a small amount of nickel. It's incredibly hot and dense, with temperatures reaching over 5,000°C (9,000°F). Although solid, the immense pressure prevents the iron from melting.

It's important to note that the outer core is a liquid layer of iron and nickel that surrounds the inner core. This liquid metal generates Earth's magnetic field.