Fast Red RL salt is widely used in histology and cytology as a chromogen in staining procedures. It is particularly effective in immunohistochemistry (IHC) for visualizing specific antigens in tissue samples. When coupled with an appropriate enzyme, such as alkaline phosphatase, it produces a vivid red precipitate, enabling clear identification of target proteins or cellular structures under a microscope. This makes it invaluable in diagnostic pathology for detecting diseases like cancer, where precise localization of biomarkers is critical. Additionally, it is employed in molecular biology for in situ hybridization techniques to detect nucleic acids. Its stability and intense color make it a preferred choice for researchers and clinicians aiming for high-contrast, reliable results in microscopic analysis.