Used primarily in histology to detect and quantify collagen fibers in tissue sections, especially in liver, heart, and skin samples. Commonly applied in research and diagnostic settings to assess fibrosis or connective tissue changes. The stain binds specifically to collagen, producing a bright red color under light microscopy, allowing for clear differentiation from other tissue components. Often used in conjunction with fast green counterstain to provide contrast. Suitable for both qualitative assessment and image analysis-based quantification of collagen deposition.