Men who experience erectile dysfunction often try to keep their predicament out of the spotlight. That may change, however, if they are able to benefit from an optogenetic therapy that triggers erections. The therapy, developed by scientists at ETH Zürich, involves the transfection of a light-reactive gene construct into erectile tissue. The construct reacts to blue light by facilitating a surge of the second messenger cyclic guanosine monophosphate, allowing voltage-dependent calcium channels to close. As a result, muscle cells relax, erectile tissue becomes engorged with blood, and the penis stiffens. The therapy, dubbed erectile optogenetic stimulation (EROS) in Angewandte Chemie, has been shown to work in rats. In humans, it may compare favorably to Viagra, which can only maintain an erection, not trigger it.