The MITO-ID® dye in the MITO-ID® Membrane potential detection kit (ENZ-51018) is a dual-emission cationic dye to measure the mitochondrial membrane potential (MMP) in live cells. In energized or active cells, the MITO-ID® Membrane Potential reagent rapidly accumulates as orange-fluorescent aggregates in the mitochondria due to their relative negative charge, while it exists as a green-fluorescent monomer in the cytosol. However, in cells with compromised MMP, the MITO-ID® Membrane Potential reagent exists primarily as green-fluorescent monomers throughout the cytosol and no longer exhibits orange fluorescence in the mitochondria.