X-ray diffraction can give us information about the structure of cryst
alline materials. Recent developments in the duration and brightness o
f X-ray sources have given rise to the potential to observe rapid chan
ges in such crystals on the picosecond, or perhaps even femtosecond ti
mescale. Time-resolved X-ray diffraction will yield new data on the ra
pid deformation of materials, biological processes, and even on chemic
al reaction kinetics.