A photomicrograph of a multicolor mixture of Molecular Probes' FluoSpheres® fluorescent microspheres overlaid with a differential interference contrast (DIC) image of the same field. Molecular Probes applies its proprietary fluorescent dye technology to produce a range of intensely fluorescent FluoSpheres® microspheres labeled with biotin, streptavidin and NeutrAvidin biotin–binding protein, providing important tools for improving the sensitivity of flow cytometry applications and immunodiagnostic assays.