Optoelectronics and molecular electronics are two areas of potential application for monolayers of ordered organic materials. These layers form spontaneously on the immersion of an appropriate substrate into a solution of an active surfactant in an organic solvent. Very strong molecule-substrate interactions result, for example between the organo-siloxane trimer and a hydroxylated surface (see figure). The build up of mono- and multilayers, the nature of the interface interactions and the applications of these organized structures are discussed.