A paradigm shift is required in chemical processing for the environmentally benign production of high quality products. To bring production systems in concert with this paradigm to reality, a new processing concept based on strict reaction control must be established. Presently, microchemical processes are expected to significantly contribute to the realization of such production systems. In a microspace, viscous force, surface tension, conduction heat transfer, and molecular diffusion become dominant. In addition, we can easily and precisely control the contact time, shape and size of the interface between fluids and so on. In this paper, studies dealing with reactions and unit operations conducted in microspace were surveyed and distinguished achievements were summarized along with the unique concepts they were based upon. The promising direction in science and technology for future microreaction technology is also discussed. (c) 2007 Elsevier Ltd. All rights reserved.