Bossi, M., Belov, V., Polyakova, S. and Hell, S. W.
Reversible red fluorescent molecular switches. Angewandte Chemie International Edition 45: 7462-7465 (2006).

Optically switchable compounds were synthesized whose visible fluorescence can be quenched down to 6 % with light at 360-400 nm and then restored with red light from a diode laser. The molecular switch offers potential applications in data storage and far-field microscopy with spatial resolution far below the diffraction limit.