The Core, BBC Documentary, Horizon

For centuries we have dreamt of reaching the centre of the Earth. Now scientists are uncovering a bizarre and alien world that lies 4, 000 miles beneath our feet, unlike anything we know on the surface. It is a planet buried within the planet we know, where storms rage within a sea of whitehot metal and a giant forest of crystals make up a metal core the size of the moon. Horizon follows scientists who are conducting experiments to recreate this core within their own laboratories, with surprising results.