Gated CW-STED microscopy: a versatile tool for biological nanometer scale investigation.

Stimulation emission depletion (STED) microscopy breaks the spatial resolution limit of conventional light microscopy while retaining its major advantages, such as working under physiological conditions. These properties make STED microscopy a perfect tool for investigating dynamic sub-cellular processes in living organisms. However, up to now, the massive dissemination of STED microscopy has been hindered by the complexity and cost of its implementation. Gated CW-STED (gCW-STED) substantially helps solve this problem without sacrificing spatial resolution. Here, we describe a versatile gCW-STED microscope able to speedily image the specimen, at a resolution below 50 nm, with light intensities comparable to the more complicated all-pulsed STED system. We show this ability on calibration samples as well as on biological samples.