Microchannel reactors consist of stacks of closely spaced thin plates designed to form microchannels with specific dimensions, regularity, and connectivity in the spaces between the plates. The advancement of this novel reaction technology requires the close link between reactor design and optimization of catalyst composition and microstructures. The inherent and unique characteristics include efficient mass and heat transfer and precise control of the hydrodynamic environment, which are often desired for distributed, mobile and intensified chemical processing. In this talk, the recent advancements in this technology and its applications will be reviewed.