Used primarily as a chromogen in immunohistochemistry and immunocytochemistry for visualizing peroxidase activity. It produces a brown precipitate when reacted with hydrogen peroxide in the presence of peroxidase, making it valuable for detecting antigens in tissue sections and cells. Also employed in enzyme-linked immunosorbent assays (ELISA) for colorimetric detection. Its sensitivity and stability make it a preferred choice in diagnostic and research applications for identifying specific proteins or cellular components.