Here's the breakdown:

* Earth's inner core is a solid ball of mostly iron and nickel, about 1,220 kilometers (758 miles) in radius. It's incredibly hot, estimated to be around 5,200°C (9,392°F).

* Earth's outer core is a liquid layer of iron and nickel surrounding the inner core, about 2,200 kilometers (1,367 miles) thick.

The presence of these two distinct cores is a result of Earth's internal structure and the intense pressure and temperature at its center.