In good STED
In stimulated emission depletion microscopy (STED) a diffraction
limited spot (top left) illuminates the sample and yields a population
of excited fluorophores (bottom left). The sample is then illuminated
with the doughnut-shaped depletion beam (top right), which deexcites
the fluorophores in the “wings” of the distribution and results
in a highly localized excited population (bottom right). The light
sources are then switched off and a high-resolution image is formed
using the photons emitted from this small region of fluorophores.