Certain common hydrogen atom transfer (HAT) cofactors (NADPH and Flavin) can operate as single electron transfer (SET) reagents.[1][14][15] Although these species are capable of HAT without irradiation, their redox potentials are enhance by nearly 2.0 V upon visible light irradiation.[16] When paired with their respective enzymes (typically ene-reductases) This phenomenon has been utilized by chemists to develop enantioselective reduction methodologies.