The dream of harnessing the power of the stars to provide near-limitless clean electricity has remained up to now just that – a dream. In stars like our own Sun, a huge amount of energy and heat is released by nuclear fusion, when the nuclei of atoms collide at very high speeds to create a new, larger nucleus. Most attempts to replicate the process in laboratories, using expensive high-density lasers or magnetic fields and super-hot plasmas, have so far struggled to get to the point at which more energy is produced than put in.