Far-Field Autofluorescence Nanoscopy

We demonstrate far-field optical imaging at the nanoscale with unlabeled samples Subdiffraaion resolution images of autofluorescent samples are obtained by depleting the ground state of natural fluorophores by transferring them to a metastable dark state and simultaneously localizing those fluorophores that are transiently returning Our approach is based on the insight that nanoscopy methods relying on stochastic single-molecule switching require only a single fluorescence on off cycle to yield an image, a condition fulfilled by various biomolecules The method is exemplified by recording label-free nanoscopy images of thylakoid membranes of spinach chloroplasts