smolloy writes "The world's first X-ray laser (LCLS) has seen first light. A Free Electron Laser (FEL) is based on the light that is emitted by accelerated electrons when they are forced to move in a curved path. The beam then interacts with this emitted light in order to excite coherent emission (much like in a regular laser); thus producing a very short, extremely bright, bunch of coherent X-ray photons. The engineering expertise that went into this machine is phenomenal — 'This is the most difficult light source that has ever been turned on,' said LCLS Construction Project Director John Galayda. 'It's on the boundary between the impossible and possible, and within two hours of start-up these guys had it right on.' — and the benefits to the applied sciences from research using this light can be expected to be enormous: 'For some disciplines, this tool will be as important to the future as the microscope has been to the past,' said SLAC Director Persis Drell."