Used as a biological stain in histology and cytology to visualize cell structures under the microscope, particularly in routine tissue examination. It imparts a pink to red color to cytoplasm and other cellular components, enabling differentiation between cell types. Commonly used as a counterstain in combination with hematoxylin in the H&E staining method, one of the most widely used techniques in diagnostic pathology. Also employed in some ophthalmic applications to stain the cornea and detect surface damage. Additionally, used in some dental products to highlight plaque and in microbiology for staining certain microorganisms.