The layer just above Earth's center is the inner core. It is the innermost layer of the Earth and is composed primarily of iron and nickel. The inner core is extremely hot, with temperatures reaching up to 5,700 degrees Celsius (10,232 degrees Fahrenheit), and is under immense pressure due to the weight of the layers above it. The inner core is solid, unlike the liquid outer core, and is believed to be the source of Earth's magnetic field.