Sample preparation for STED microscopy.

Since the discovery of the diffraction barrier in the late nineteenth century, it has been commonly accepted that with far-field optical microscopy it is not possible to resolve structural details considerably finer than half the wavelength of light. The emergence of STED microscopy showed that, at least for fluorescence imaging, these limits can be overcome. Since STED microscopy is a far-field technique, in principle, the same sample preparation as for conventional confocal microscopy may be utilized. The increased resolution, however, requires additional precautions to ensure the structural preservation of the specimen. We present robust protocols to generate test samples for STED microscopy. These protocols for bead samples and immunolabeled mammalian cells may be used as starting points to adapt existing labeling strategies for the requirements of sub-diffraction resolution microscopy.