High-resolution 3D light microscopy with STED and RESOLFT

This chapter discusses the simple yet powerful ideas which have allowed to break the diffraction resolution limit of lens-based optical microscopy. The basic principles and standard implementations of STED (stimulated emission depletion) and RESOLFT (reversible saturable/switchable optical linear (fluorescence) transitions) microscopy are introduced, followed by selected highlights of recent advances, including MINFLUX (minimal photon fluxes) nanoscopy with molecule-size (~1 nm) resolution