The deepest layer of Earth is the inner core. It is a solid ball of mostly iron with a radius of about 1,220 kilometers (758 miles).

Here's a breakdown of Earth's layers from surface to center:

* Crust: The outermost layer, thin and rocky.

* Mantle: The thickest layer, made of hot, dense rock.

* Outer core: Liquid layer of iron and nickel.

* Inner core: Solid ball of iron and nickel.