Photoactivated Localization Microscopy (PALM, or
fPALM), is a super-resolution imaging technique that
utilizes sequential activation and time-resolved localization of
photoswitchable fluorophores to create high resolution images. During
imaging, only an optically resolvable subset of fluorophores is
activated to a fluorescent state at any given moment, such that the
position of each fluorophore can be determined with high precision by
finding the centroid position of the single-molecule images. The
fluorophore is subsequently deactivated, and
another subset is activated and imaged. Iteration of this process
allows numerous fluorophores to be localized and a super-resolution
image to be constructed from the image data. PALM and fPALM were described using photoswitchable fluorescent proteins.