Used in cell biology and microbiology for distinguishing live and dead cells in a sample. The kit combines two fluorescent dyes—acridine orange (AO) and ethidium bromide (EB)—to differentially stain cells based on membrane integrity. Acridine orange penetrates all cells and emits green fluorescence in live cells by binding to RNA and DNA, while ethidium bromide only enters cells with damaged membranes, producing red-orange fluorescence in dead cells by intercalating into DNA. This dual-staining method allows rapid assessment of cell viability under a fluorescence microscope, commonly applied in apoptosis studies, cytotoxicity testing, and microbial viability assays. The technique is valued for its speed, sensitivity, and ability to provide visual confirmation of cell status in research and diagnostic settings.