The technique of JC-1 staining has been developed with the intent to detect DY in intact, viable cells. For this purpose JC-1 acts as a marker of mitochondrial activity, since the formation of J-aggregates, which give red emission, is reversible. Cells with high DY are those forming J-aggregates, thus showing high red fluorescence. On the other hand, cells with low DY are those in which JC-1 maintains (or re-acquire) monomeric form, thus showing only green fluorescence.