Antibodies sometimes bind to intracellular components due to nonspecific protein-protein interaction, and to fat due to hydrophobic interaction, and may also bind to antibody receptors on some cell surfaces. In order to eliminate the background staining caused by the nonspecific binding of antibodies to cells, all antibodies of the same subtype that have nothing to do with antigens can be compared, that is, Isotype control. Homotypic control generally selects antibodies with the same species source, subtype and fluorescence label as the corresponding antibodies. In terms of dosage, the isotype control equivalent to microgram of corresponding antibody should be added.