The fluorescent antibody technique is a laboratory method that uses fluorescently labelled antibodies to detect specific antigens in tissues or cells, allowing for visualisation under a fluorescence microscope. This technique is crucial in clinical practice for diagnosing infections, autoimmune diseases, and certain cancers by identifying the presence of pathogens or abnormal cells. A key example is its use in diagnosing viral infections, such as rabies, through the detection of viral antigens in tissue samples.