High-resolution fluorescence imaging has a vast impact on our understanding of intracellular organization. The
key elements for high-resolution microscopy are reversibly photo-switchable fluorophores that can be cycled
between a fluorescent and a non-fluorescent (dark) state and can be localized with nanometer accuracy. For
example, it has been demonstrated that conventional cyanine dyes (Cy5, Alexa647) can serve as efficient photoswitchable
fluorescent probes. We extended this principle for carbocyanines without the need of an activator
fluorophore nearby, and named our approach direct stochastic optical reconstruction microscopy (dSTORM).
Recently, we introduced a general approach for superresolution microscopy that uses commercial fluorescent
probes as molecular photoswitches by generating long lived dark states such as triplet states or radical states.
Importantly, this concept can be extended to a variety of conventional fluorophores, such as ATTO520, ATTO565,
or ATTO655. The generation of non-fluorescent dark states as the underlying principle of superresolution
microscopy is generalized under the term photoswitching microscopy, and unlocks a broad spectrum of organic
fluorophores for multicolor application. Hereby, this method supplies subdiffraction-resolution of subcellular
compartments and can serve as a tool for molecular quantification.