The development of X-ray source brilliance has been dramatic since the introduction of the first generation accelerators based sources of synchrotron radiation some 50 years ago. The latest phase in this development, the free electron lasers (FEL) has offered a billionfold leap in brilliance. Free electron lasers offer:
and they materialize previously undreamed-of possibilities for research in new domains of power density and time scale. Following the first VUV FEL (FLASH) at Hamburg in 2006 and the first X-ray FEL (LCLS) at Stanford in 2009 the science community is presently acquiring an entirely new toolbox to unravel the structure and dynamics of materials at the atomic scale.