The half-cell reduction potential of the GSSG,2H+/2GSH couple correlates, or more likely determines, the biological state of the cell (6). The state of the GSH redox buffer can turn molecular switches on and off, leading to different biological states. The redox state of this buffer as well as related redox couples, such as the cystine,2H+/2cysteine couple, can inform approaches to interventions to improve health. Note that quiescence is a reversible state; cells can re-enter the cell cycle and proliferate. Differentiation is not reversible.