Nanoscopy

Nanoscopy refers to optical imaging techniques that surpass the diffraction limit to resolve structures at the nanometer scale. While conventional light microscopy is limited to about 200–250 nanometers, nanoscopy can reach tens of nanometers or better, enabling visualization of cellular components with high precision. Techniques fall into two broad categories: those that engineer the point-spread function and localize single molecules, and methods that physically expand the specimen.

STED uses a depletion beam to suppress fluorescence around the excitation spot, narrowing the effective focal region. PALM and STORM localize individual, photo-switchable molecules and reconstruct a high-resolution image from many cycles. SIM uses patterned illumination to extract higher spatial frequencies, typically doubling resolution with fast imaging. MINFLUX achieves nanometer localization with minimal photon flux. Expansion microscopy physically enlarges the specimen so conventional microscopes can resolve features beyond their native limits.

Applications include cell and neurobiology, and materials science, enabling visualization of organelles, protein complexes, and molecular arrangements in situ. Limitations include the need for specialized equipment, labeling, photobleaching, and trade-offs among speed, resolution, and phototoxicity. Nanoscopy complements electron microscopy by providing molecularly specific imaging in relatively intact, hydrated samples.