1. Crust: This is the outermost and thinnest layer, composed of solid rock. It's what we live on and where we find mountains, valleys, and oceans.

2. Mantle: This is the thickest layer, made of mostly solid rock, but it behaves like a very viscous fluid over long periods. The mantle is responsible for plate tectonics and volcanic activity.

3. Core: This is the Earth's innermost layer, composed of mostly iron and nickel. It's divided into a liquid outer core and a solid inner core. The core is responsible for the Earth's magnetic field.