Here's a breakdown:

* Crust: This is the outermost layer, and it's incredibly thin compared to the other layers. It's made up of mostly rock and is divided into oceanic crust (thinner and denser) and continental crust (thicker and less dense).

* Mantle: This is the thickest layer, making up about 84% of Earth's volume and 67% of its mass. It's mostly solid rock, but it can behave like a very viscous fluid over long periods.

* Outer Core: This is a liquid layer composed mostly of iron and nickel. It's responsible for Earth's magnetic field.

* Inner Core: This is a solid ball of iron and nickel at the center of Earth. It's incredibly hot and dense.

While the inner core is extremely dense, the sheer size of the mantle makes it far more massive than the crust.