How do you see something smaller than the wavelength of light itself? Fluorescence microscopy is the most common optical technique used for visualizing cellular functions. The latest techniques allow labeling of specific organelles and proteins with molecular precision. But conventional microscopy cannot resolve objects closer than 200 nanometers at the focal plane. Many subcellular structures and groups of proteins occur on the 10 nanometer scale. A true understanding of cellular physiology requires new superresolution methods.

Of these methods, PALM (Photoactivated Localization Microscopy) provides the highest shown resolution in biological samples (approximately 10 nanometers) and allows for the assessment of individual molecules. In the December issue of Cold Spring Harbor Protocols, Oregon Health Science University’s Haining Zhong presents Photoactivated Localization Microscopy (PALM): An Optical Technique for Achieving ~10-nm Resolution. The article provides an overview of the basic principles of PALM, its implementation and the potential applications in neuroscience.