Photochromic reactions can induce reversible changes in morphorogy, physical state, orientation of molecular assemblies. This review describes photoinduced events in liquid crystals, polymeric liquid crystals, Langmuir-Blodgett films, micelles, bilayer membranes and gels. Azobenzene is the most widely employed photochromic unit as the trigger. These phenomena possess potential appcilability toward fabrication of new optical recording media, transducers of optical information, etc., and hence works in this field are rapidly developing.