Used in histology and pathology laboratories to selectively stain mast cells in tissue sections. The solution helps identify mast cell granules, which contain heparin and other mediators, by metachromatically staining them purple or reddish-purple under microscopic examination. This staining technique is particularly valuable in diagnosing mast cell-related disorders such as mastocytosis or systemic mast cell activation. It is also applied in research settings to study inflammatory responses, allergic reactions, and connective tissue diseases where mast cell proliferation or degranulation is a key feature. The method is favored for its simplicity, reliability, and high contrast in tissue morphology.