2′-anilino-6′-[ethyl(3-methylbutyl)amino]-3′-methylspiro[isobenzofuran-1(3H),9'-[9H]xanthene]-3-one, with the molecular formula C36H39NO3, is employed as a fluorescent dye in biological staining and fluorescence microscopy. Its distinctive characteristics enable precise visualization and imaging of biological structures, contributing to advancements in biomedical research and diagnostics.