The structure and characteristics of AOT (aerosol OT, sodium bis(2-ethylhexyl) sulfosuccinate)-water-isooctane reverse micellar microreactors have been studied by means of electrical conductivity, infrared spectra (IR), nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC). The influences of temperature and organic additive are discussed. Nanometre-sized Fe3O4 and ZnS particles are prepared by reaction in the microreactors and the properties of the obtained nanoparticles are studied with the help of a transmission electron microscope (TEM) and ultraviolet (UV) spectra, respectively. (C) 1998 Elsevier Science S.A. All rights reserved.