We know what 4% of the Universe is made of. But what about the rest? There was a time, not so long ago, when science seemed to understand how the universe worked. Everything – us, the Earth, the stars and even exotic-sounding supernovae – was made of atoms which were all created at time-zero: the Big Bang. In between the atoms was nothing, a void: quite literally, 'space'. But recently things have started to unravel. There is, it seems, a lot more to the universe than meets the eye. According to the best estimates, we only really know what about 4% of it is made of. But if only 4% is made of atoms, what about the rest? The rest is made of mysterious entities about which very little is understood, with equally mysterious names: dark matter and dark energy.