The four major layers of the Earth from exterior to interior are:

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Think about how Earth is built from the outside in. The crust is the outermost solid shell we live on, though it’s relatively thin. Beneath it lies the mantle, a much thicker layer of rock that behaves plastically over long timescales. Below the mantle is the outer core, which is a liquid layer of iron and nickel; its motion generates Earth’s magnetic field. At the center sits the inner core, a solid sphere kept solid by immense pressures. So the order from exterior to interior is crust, mantle, outer core, inner core. If a sequence swapped the crust and mantle or placed the inner core above the outer core, it would contradict what seismic and geophysical data tell us about these boundaries and states.