Used as a fluorescent dye in biological staining, particularly for visualizing acidic compartments in cells such as lysosomes. It is commonly applied in fluorescence microscopy to track endocytic pathways and monitor autophagy. Its ability to accumulate in acidic organelles makes it a valuable tool for studying cellular degradation processes and organelle dynamics. Also utilized in flow cytometry for cell viability assessment and apoptosis detection due to its pH-dependent fluorescence properties.