Explore the development and principles of Photo Activated Localization Microscopy (PALM) in this 34-minute conference talk presented by Harald Hess from Janelia Research Campus at the APS March Meeting 2015 Kavli Foundation Special Symposium: Frontiers of Light. Trace the journey from the initial inspiration drawn from Near-field Scanning Optical Microscopy (NSOM) and single-molecule imaging to the breakthrough discovery of switchable fluorescent proteins. Gain insights into the technical challenges overcome and the potential biological applications of this super-resolution imaging technique. Understand how PALM achieves sub-diffractive accuracy by activating and localizing subsets of fluorescent labels, and learn about the ongoing efforts to demonstrate its biological relevance.