  Super-resolution localization microscopy is based on determining the
positions of individual fluorescent markers in a sample. The major challenge in
reaching an ever higher localization precision lies in the limited number of
collected photons from single emitters. To tackle this issue, it has been shown
that one can exploit the increased photostability at low temperatures, reaching
localization precisions in the sub-nanometer range. Another crucial ingredient
of single-molecule super-resolution imaging is the ability to activate
individual emitter within a diffraction-limited spot. Here, we report on
photoblinking behavior of organic dyes at low temperature and elaborate on the
limitations of this ubiquitous phenomenon for selecting single molecules. We
then show that recording the emission polarization not only provides access to
the molecular orientation, but it also facilitates the assignment of photons to
individual blinking molecules. Furthermore, we employ periodical modulation of
the excitation polarization as a robust method to effectively switch
fluorophores. We bench mark each approach by resolving two emitters on
different DNA origami structures.
