Microparticles are particles between 0.1 and 100 ?m in size. Commercially available microparticles include those made of glass, latex, polystyrene, various metals (carbon, silver, copper, etc.), and various magnetic materials. Microparticles have been found to have widespread applications in medicine, biochemistry, colloid chemistry, and aerosol research. Uses include chromatographic separation media, supports for immobilized enzymes, and spacers in liquid crystal displays Monodisperse melamine resin particles are a new class of polymer particles with excellent physical and chemical properties. Polystyrene nano- and microspheres particles are typically used for calibration purposes and immunoassays (latex agglutination test, FACS). Many of the tests are based on non-covalent binding of specific antibodies, antigens or cells to the hydrophobic particle surface. Covalent attachment of proteins to surface modified particles is possible .