Rhodamine 123 is widely used as a fluorescent dye in biological and medical research. It is particularly valued for its ability to selectively stain mitochondria in living cells, making it a crucial tool for studying mitochondrial function and dynamics. Researchers use it to assess cell viability, monitor membrane potential, and investigate cellular respiration. In cancer studies, it helps identify drug-resistant cells by analyzing their mitochondrial activity. Additionally, it is employed in flow cytometry and fluorescence microscopy to visualize and analyze cell populations. Its stability and bright fluorescence make it a reliable choice for tracking cellular processes in real-time.