Light-induced dark states of organic fluochromes enable 30 nm resolution imaging in standard media.

We show that high quantum efficiency fluorophores can exhibit reversible photobleaching. This observation provides the basis for an imaging technique we call reversible photobleaching microscopy. We demonstrate applicability of this technique using antibody labeled biological samples in standard aqueous (or glycerol based) media to produce far-field images at approximately 30 nm resolution. Our novel method relies on intense illumination to reversibly induce a very long-lived (>10 s) dark state from which single fluorochromes slowly return stochastically. As in other localization microscopy methods, reversible photobleaching microscopy localizes single fluorochromes, but has the advantage that specialized photoactivatible and photoswitchable molecules or special immersion/embedding media are not required.