Radiation pulses from Q‐switched lasers can be used to transiently melt and modify the near surface regions of solids. Indeed the annealing is of such short duration that new, extremely rapid solidification phenomena are now amenable to study. Most work has probed the basic crystal growth behavior of elemental Si. This process is often strongly influenced by the presence of high concentrations of impurities: either growth instabilities or metastable, supersaturated solid solution formation may occur. At the highest resolidification rates (≳10 m/s) the recrystallization interface can break down with the formation of an amorphous solid phase. This paper describes the various processes which can occur and identifies limiting behavior in high speed crystal growth.