PHYSICS OF COLLOIDS IN SPACETHE PROPOSED EXPERIMENTS WILL PROVIDE A UNIQUE EXAMPLE OF THE USE OF COLLOIDAL ENGINEERING TO SYNTHESIZE NEW MATERIALS WITH NOVEL PROPERTIES. THE GOAL IS TO EXPLOIT THE LONG RANGE ORDERED STRUCTURES FORMED USING THE SELF-ASSEMBLY OF COLLOIDAL PARTICLES. THIS PROVIDES AN OPPORTUNITY TO SYNTHESIZE STRUCTURES THAT ARE ORDERED ON THE LENGTH SCALE OF LIGHT IN ALL THREE DIMENSIONS AND SUCH MATERIALS SHOULD HAVE VALUABLE NEW PROPERTIES. FOR EXAMPLE THEY MAY BE SUITABLE FOR OPTICAL SWITCHES OR FILTERS OR AS PHOTONIC BAND GAP MATERIALS. THE USE OF COLLOIDAL MATERIALS IN MICROGRAVITY ALLOWS THE STRUCTURES TO BE SELF-ASSEMBLED PROVIDING A NEW METHOD FOR MATERIALS SYNTHESIS WHERE TRADITIONAL LITHOGRAPHIC METHODS ARE VERY DIFFICULT AND HAVE NOT BEEN DONE ON THE OPTICAL LENGTH SCALE. A MICROGRAVITY ENVIRONMENT REMOVES THE LIMITATIONS IMPOSED BY SEDIMENTATION. THIS ALSO ENABLES THE STUDY OF MIXTURES OF COLLOIDS AND POLYMERS WHERE THE ADDITION OF POLYMER INDUCES WEAK ATTRACTIVE INTERACTIONS BETWEEN THE COLLOIDAL PARTICLES BY THE DEPLETION ATTRACTION MECHANISM. THIS ALLOWS THE STUDY OF MODEL CRITICAL FLUIDS WITHOUT THE EXTREMELY DIFFICULT TEMPERATURE CONTROL NEEDED WITH OTHER APPROACHES.