Used in histology and microscopy to enhance the staining contrast of hematoxylin-stained tissue sections. It helps convert hematoxylin to its active form, improving nuclear staining clarity and producing a sharp blue to blue-black color in cell nuclei. Commonly applied in routine tissue examination, this reagent is essential in diagnostic pathology and research for achieving consistent and high-contrast staining results. It is particularly useful after acidic staining steps to "blue" the tissue sections by adjusting the pH, ensuring optimal visualization under the microscope.