PHOTO ACTIVATED LOCALIZATION MICROSCOPY (PALM)

Photo activated localization microscopy (PALM) is a widefield fluorescence microscopy imaging methods that allow obtaining images with a resolution beyond the diffraction limit. PALM is based on collecting a large number of images each containing just a few active isolated fluorophores. The imaging sequence allows for the many emission cycles necessary to stochastically activate each fluorophore from a non-emissive state to a bright state, and back to a bleached state. During each cycle, the density of activated molecules is kept low enough that the molecular images of individual fluorophores do not typically overlap.