Stochastic optical reconstruction microscopy (STORM) is a high-resolution fluorescence microscopy technique that achieves sub-diffraction-limit resolution by precisely localizing photo-switchable fluorophores. The method involves switching fluorophores on and off using different colored light, allowing their positions to be determined with nanometer accuracy. By repeating this process over multiple cycles, the positions of many fluorophores are determined, enabling the reconstruction of a high-resolution image. The technique demonstrated a resolution of approximately 20 nm, which is 10 times better than conventional fluorescence microscopy. STORM uses a cyanine dye switch, which can be toggled between a fluorescent and dark state by red and green lasers. This switch allows for the localization of individual fluorophores with high accuracy. The resolution of STORM is limited by the accuracy of individual switch localization during a switching cycle. The technique was tested on DNA samples, where it successfully resolved switches separated by 40 nm, demonstrating its ability to image biological structures with sub-diffraction-limit resolution. STORM offers a distinct advantage in localizing a large number of switches within a diffraction-limited spot, making it a general biological imaging technique. It was used to image RecA filaments, revealing their circular structure with greatly increased resolution compared to wide-field images. The technique is also applicable to other photo-switchable fluorophores and fluorescent proteins, potentially enabling high-resolution live-cell imaging with endogenous labels. The resolution of STORM is theoretically limited by the number of photons emitted per switch cycle, not the wavelength of light. The technique has the potential to be a valuable tool for high-resolution fluorescence in situ hybridization (FISH) and immunofluorescence imaging. The method was supported by grants from the National Institute of Health, the Defense Advance Research Projects Agency, and a Packard Science and Engineering Fellowship.Stochastic optical reconstruction microscopy (STORM) is a high-resolution fluorescence microscopy technique that achieves sub-diffraction-limit resolution by precisely localizing photo-switchable fluorophores. The method involves switching fluorophores on and off using different colored light, allowing their positions to be determined with nanometer accuracy. By repeating this process over multiple cycles, the positions of many fluorophores are determined, enabling the reconstruction of a high-resolution image. The technique demonstrated a resolution of approximately 20 nm, which is 10 times better than conventional fluorescence microscopy. STORM uses a cyanine dye switch, which can be toggled between a fluorescent and dark state by red and green lasers. This switch allows for the localization of individual fluorophores with high accuracy. The resolution of STORM is limited by the accuracy of individual switch localization during a switching cycle. The technique was tested on DNA samples, where it successfully resolved switches separated by 40 nm, demonstrating its ability to image biological structures with sub-diffraction-limit resolution. STORM offers a distinct advantage in localizing a large number of switches within a diffraction-limited spot, making it a general biological imaging technique. It was used to image RecA filaments, revealing their circular structure with greatly increased resolution compared to wide-field images. The technique is also applicable to other photo-switchable fluorophores and fluorescent proteins, potentially enabling high-resolution live-cell imaging with endogenous labels. The resolution of STORM is theoretically limited by the number of photons emitted per switch cycle, not the wavelength of light. The technique has the potential to be a valuable tool for high-resolution fluorescence in situ hybridization (FISH) and immunofluorescence imaging. The method was supported by grants from the National Institute of Health, the Defense Advance Research Projects Agency, and a Packard Science and Engineering Fellowship.