Primary antibody
Primary antibodies can be used in conjunction with secondary antibodies as an extrinsic label in microscopic imaging. The primary antibodies are infused into a permeabilised cell/ tissue. They react with a complementary secondary antibodies which are fluorescently labelled. This technique is called immunoflourescence microscopy which is used in protein localisation studies. (Alberts et al 2002 Molecular Biology of the cell 5th , (9)588-589)