Medieval alchemists wrote of a mysterious fountain of youth, whose waters could rejuvenate anyone who drank them. But can water really be magical? In the second of this year's Christmas Lectures, Dr Peter Wothers drinks from the fountain and finds out whether the elements lurking in the water can restore his youth. Along the way he discovers how exploding balloons could solve the energy crisis, how water contains the remains of the most violent reactions on Earth and that the real secret to eternal youth might be drinking no water at all. Peter is joined in his quest by Paralympic champion cyclist Mark Colbourne and finds out what happens when the two most reactive elements on the periodic table, caesium and fluorine, meet each other.