Microemulsions are very versatile reaction media which nowadays find many applications, ranging from nanoparticle templating to preparative organic chemistry. On one hand, for the synthesis of nanomaterials microemulsions represent a well-established technique that can be used to fine control the particle size of many inorganic and organic materials, as well as latexes. On the other hand, the thermodynamical stable and microheterogeneous nature of microemulsions, used as reaction media, induces drastic changes in the reagent concentrations, and this can be specifically used for tuning the reaction rates. In particular, amphiphilic organic molecules can accumulate and orient at the oil–water interface inducing regiospecificity in organic reactions. In this review, we will show the recent tendencies of the use of microemulsions for the preparation of nanoparticles, and also as particularly interesting organic reaction media.