Fluorescent detection is a technique used in immunohistochemistry to visualize multiple antigens simultaneously. It is based on the use of fluorophores that emit light when excited by a light source. The fluorophore is conjugated to the primary antibody for direct detection and to the secondary antibody for indirect detection. 

• Weaker signal strength results in lower sensitivity indirect detection can be used to amplify enzyme-conjugated antibodies to enhance sensitivity. 
• Fluorescent signals are vulnerable to photobleaching and may diminish on prolonged exposure to light.