Chromogenic detection is a technique used in immunohistochemistry to visualize the presence of antigens in tissue. It is based on the chemical reactions produced by enzymes (either HRP or AP) conjugated with either the primary or secondary antibody.  

• Indirect chromogenic detection amplifies signals, boosting their strength for enhanced sensitivity. 
• Chromogenic stains have higher resistance to photobleaching as compared to fluorochromes, which helps to generate longer-lasting signals.