Summary form only given. Recently developed ultrafast laser-driven X-ray sources enable the observation of atomic motions in crystals and in solutions on the timescale of chemical bond formation and breakage. Using such a laboratory-based X-ray source the propagation of coherent phonon wave packets through GaAs(111) crystals after photo excitation has been imaged by ultrafast X-ray difraction. While ultrafast x-ray diffraction measures the structural dynamics of crystals, ultrafast extended x-ray absorption line structure (UEXAFS) can, in principle, measure the structural dynamics of atoms during a chemical process in solution.