Stimulated emission depletion (STED) microscopy is a superresolution microscopy technique that overcomes the resolution barrier of conventional light microscopy. Using a donut-shaped depletion laser the effective focal excitation spot is reduced beyond Abbe’s diffraction limit. Under optimal conditions, resolution is improved from 200 nm to less than 40 nm. STED microscopy is suited for both fixed specimen and living samples. Data is acquired and analyzed in real time. A multitude of established dyes are suited for this technique. However, superior results are expected by using specialized dyes that show improved photostability.
The Leica tau-STED technology is based on the combination of fluorescence intensity and fluorescence lifetime information. The STED depletion laser reduces the lifetimes of fluorophores depending on their distance from the focus point. This further improves the signal-to-noise ratio.