Whether ELISA, chemokine/cytokine assay, radioimmunoassay, drug screening, or one of the other hundreds of other applications, the immunoassay is one of the most powerful procedures in biological science. It harnesses the exquisite sensitivity of the immune system to find and reveal the presence of a molecule, even in vanishingly small quantities. Antibodies are used to bind to the target molecule, and then in turn bind to a dye or other visualization agent. The possible combinations are endless. Immunoassays are used everywhere from basic bench research to the clinical diagnostic laboratory. One of the most important considerations in purchasing immunoassay products are the quality and purity of reagents, especially antibodies.