The fast and convenient heating of foodstuffs in microwave ovens is routinely used in the common life. Recently, many researchers have recognized other potential applications for this method of heating, then have applied the rapid and selective heating associated with microwave technology to a number of useful processes. With the tool of the basic information required to apply the microwave technology to many processes, this paper reviewed briefly the principle and characteristic of microwave heating, the design of microwave unit, the interaction of microwave-matter, and the outlook of future microwave technology. Especially, it is focussed to explain the microwave thermal and nonthermal effects in organic synthesis based on medium effects and mechanistic considerations.