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Helium is the second most abundant element in the universe but very rare on earth. Professor Andrea Sella of University College London, explains to Justin Rowlatt the properties that make this inert gas so useful. He explains where it comes from and where it goes to.

Washington correspondent, Jonny Dymond, is out in the wilds of the Texas pan-handle to explore the US national helium reserve. And, we hear from the head of General Electric's Magnetic Resonance Imaging division - one of the world's biggest users of helium - on why the gas is so important in the fight against many diseases.