Professor Selvin did two sets of experiments during his postdoctoral training. One was developing a new type of fluorescence resonance energy transfer (FRET) based on lanthanides, called luminescence resonance energy transfer (LRET). He later used this technique to discover how a potassium ion channel, in part responsible for nerve conduction, responds to voltage (Cha, 1999, Nature; Posson, 2005, Nature). The second involved single molecule fluorescence—the first measurement of FRET between a single donor and single acceptor (Ha, 1996, PNAS).