Light Microscopy

STED (stimulated-emission-depletion) microscopy is scanning fluorescence microscopy in which the illumination is shaped ( doughnut-shaped) to exceed the resolution limit imposed by diffraction. This limit is exceeded by using stimulated emission (592 nm and 660 nm ) to eliminate fluorescence in the outer regions of the excitation optical impulse response. The width of the central zone that can still emit light is adjusted by saturating the fluorescence. In practice, we achieve resolutions of the order of 50 nm, but in theory there is no limit to how low the resolution threshold can be.