Developments in basic physics are commonly related to advances in technology and in measurement techniques. Sometimes new methods of measurement open up new branches of knowledge end at other times the new techniques follow. One example is the development of high-power frequency tunable dye-lasers which has permitted the selective excitation of atoms and molecules and the recording of absorption spectra from excited states. With the extension of tunable lasers into the ultraviolet these new spectroscopic techniques can be applied to a wide range of transitions. The recent advances in direct time measurements in the picosecond range provide a second example. These have been made possible by the availability of intense ultra-short pulses of light from mode-locked lasers. It is thus now possible to investigate on a picosecond time-scale the interactions of light with matter. The present state of the art in both of these fields is reviewed with particular reference to electron optical streak-camera measurements and to experiments employing frequency-tunable, picosecond pulses from mode-locked dye lasers. Applications considered include compression of matter to very high densities and temperatures, for thermonuclear fusion, and photo-chemistry.