One of the major accomplishments of laser technology that took place dur ing the last 15 years is the possibility of generating coherent radiation that 18 can be focused so that its intensity reaches the magnitude of 10 W/ern." Even higher intensities result from nonlinear self-focusing of such radiation in matter. The unique character of these magnitudes is illustrated by the fact that these intensities are substantially higher than those occurring inside the Sun. A range of previously unexplored physical mechanisms come into playas laser pulses interact with matter under the conditions of...