What? I had the audacity to call the Earth a pebble? But our planet is huge, right? Not really. Well, it is compared to a human, and a human is gigantic compared to an ant. It's all matter of perspective. Check out this image:
Beneath the mantle is a layer called the outer core. It is made up by liquid metals that move, in turn creating the magnetosphere that stretches several thousand kilometers above the surface.
What's under the outer core? I'm happy you asked. Since there's an outer core it stands to reason we also have an inner core. This is believed to consist of an iron-nickel alloy that has about the same temperature as the surface of the sun. It stays solid because of the tremendous pressure.