Coloured scanning electron micrograph (SEM) of nuclear fusion laser targets. These silicon spheres, which measure approximately 50 micrometres in diameter, are filled with a mixture of the hydrogen isotopes deuterium and tritium. When a laser beam is focused on a pellet containing these spheres the high temperature and pressure created causes the isotopes to fuse, forming helium nuclei. This process releases massive amounts of energy. If this process can be harnessed it could be an unlimited source of clean renewable energy.