Molecular Level Super-Resolution Fluorescence Imaging.

Over the last 30 years, fluorescence microscopy, renowned for its sensitivity and specificity, has undergone a revolution in resolving ever-smaller details. This advancement began with stimulated emission depletion (STED) microscopy and progressed with techniques such as photoactivatable localization microscopy and stochastic optical reconstruction microscopy (STORM). Single-molecule localization microscopy (SMLM), which encompasses methods like direct STORM, has significantly enhanced image resolution. Even though its speed is slower than that of STED, SMLM achieves higher resolution by overcoming photobleaching limitations, particularly through DNA point accumulation for imaging in nanoscale topography (DNA-PAINT), which continuously renews fluorescent labels. Additionally, cryo-fluorescence microscopy and advanced techniques like minimal photon fluxes imaging (MINFLUX) have pushed the boundaries toward molecular resolution SMLM. This review discusses the latest developments in SMLM, highlighting methods like resolution enhancement by sequential imaging (RESI) and PAINT-MINFLUX and exploring axial localization techniques such as supercritical angle fluorescence and metal-induced energy transfer. These advancements promise to revolutionize fluorescence microscopy, providing resolution comparable to that of electron microscopy.