MitoSpy™ Orange, MitoSpy™ Red, and MitoSpy™ NIR localize to the mitochondria based on its membrane potential. This potential is created by the transport of ions across the membrane. Thus, MitoSpy™ Orange, MitoSpy™ Red, and MitoSpy™ NIR work well to indicate cell health as well as localization. On the other hand, MitoSpy™ Green FM’s attraction to the mitochondria is not based on membrane potential. While the full mechanism of MitoSpy™ Green FM is not yet understood, it may have to do with homology between the reagent’s structure and proteins at the mitochondrial surface. Because of this reagent’s membrane potential independence, it can be used to measure mitochondrial mass of individual cells in flow cytometry.