The invention of the laser in 1961 heralded a revolution in optics. Here was a source which was so coherent and monochromatic that it made possible a host of applications from CD players to surveying instruments. But the power delivered was usually very modest. Now, scientists at the Lawrence Livermore Laboratory have tested what is by far the most powerful laser in the world. Named the Petawatt laser, it delivers about 1,000 trillion watts of energy! That may sound like a lot of energy but it is delivered in pulses about half a trillion seconds long. The laser is part of a new scheme for laser induced thermonuclear fusion reactions.