The synthetic reaction for the formation of various kinds of nanoparticles such as ITO, fluorescent materials, conducting polymers was carried out in surfactant solutions. Surfactant molecules are self-assemblied into a monodispersed aggregates of certain size and shape in aqueous solution depending upon the surfactant concentration, the presence of salt, pH and temperature. Since the reaction for particle formation is confined into the surfactant aggregate, the size of particles can not exceed that of surfactant aggregates and the particle shape would by influenced by that of aggregates.