Working under supercritical conditions at microscale combines the advantages of size reduction provided by microsystems to the unique properties of supercritical fluids (SCFs). The so-called "supercritical microfluidics" therefore addresses the limitations of both macroscale SCFs reactors and conventional liquid microfluidic reactors. In this review, we present recent developments in supercritical microfluidics processes with the design of microreactors capable of working under pressure and temperature, some general characteristics of supercritical microflows and, through selected examples, flow-through chemistry and nanocrystals synthesis in supercritical microreactors. (c) 2011 Elsevier B.V. All rights reserved.