The evolution of the microemulsion technique in the last years is revised with special emphasis in the mechanisms of control of particle size, namely the control by the proper microemulsions and the control by the surfactant adsorption (capping). The kinetics of the particle formation; the possibility of the preparation of coatings, core-shell and ‘onion-like’ structures with a very precise size control; the use of microemulsions to produce fine ceramics and finally their use in the preparation of superlattices is addressed.