Ponceau S is widely used as a biological stain, particularly in biochemistry and molecular biology. It is commonly employed to stain proteins on polyacrylamide gels after electrophoresis, allowing for the visualization of protein bands. This stain is favored for its sensitivity and ease of use, as it quickly binds to proteins and provides a vivid red or pink color, making it easier to analyze protein patterns. Additionally, Ponceau S is often used as a temporary stain to verify protein transfer efficiency in Western blotting before proceeding with antibody-based detection. Its reversible nature allows it to be washed off, ensuring it does not interfere with subsequent steps. Beyond protein staining, it is also used in histological applications to differentiate tissue components under microscopic examination.