Reactions in micro-heterogeneous systems have been found to be of great interest in the past few decades. Two such micro-heterogeneous aggregates are micelles and reverse micelles, which are formed by surface active agents or surfactants. In numerous chemical reactions, the use of these systems as microreactors increases the rate of the reaction up to 10-100 folds. This chapter will be concentrated on micelles and reverse micelles as catalytic reactors since, in the past few decades, numerous numbers of reactions have been successfully carried out in these systems.