<title>Time-resolved techniques: an overview</title>

Techniques for time-resolved X-ray scattering on time scales varying from kiloseconds to picoseconds are reviewed. It is concluded that the pulsed time structure and the high photon fluxes available from synchrotron X-ray sources provide new opportunities for time-resolved X-ray scattering investigations. Synchrotron beams typically consist of subnanosecond pulses of X-rays separated in time by a few tens of nanoseconds to a few hundred nanoseconds so that these beams appear as continuous X-ray sources for investigations of phenomena on time scales ranging from hours down to microseconds. Studies requiring time-resolution in the microsecond range can be carried out in a triggering mode by stimulating the phenomenon under consideration in coincidence with the X-ray pulses. Time resolution on the picosecond scale can be achieved through streak camera techniques in which the time structure of the individual X-ray pulses are viewed as quasi-continuous sources with about 100-200 picoseconds duration.