Flash-boiling atomization is one of the most effective means of generating a fine and narrow-dispersed spray. Owing to its complexity its potential has not been fully realized to date. The paper reviews the present knowledge of the different mechanisms involved in the flash-boiling atomization process. These include intense nucleation, fast bubbles' growth and liquid atomization. The inter-relationships between the distinctive processes determine the spray quality. Recent experimental observations and physical interpretations have improved our insight and led to better understanding of the whole process. One practical result is the establishment of design criteria for an optimal flash-boiling atomizing system.