Super resolution fluorescence microscopy has become essential for cell biology studies. The recent advence of superresolution microscopies such as Stimulated Emission Depletion (STED microscopy, invented by Stefan Hell, Nobel Prize for Chemistry 2014) has revolutionized observation of biological samples, enabling lateral resolution of a few tens of nanometers on fixed or immobile samples, at first, then more recently on living cells. One advantage of STED compared to other superresolution optical methods is that a superresolution image is obtained rapidly with no need for data processing following acquisition. STED therefore represents a perfect tools to obtained on the nanometer scale and now in 3D (70nm in the 3 directions) and in multi-color. Here, we will apply this multicolor 3D nanotechnology to very small biological objects like fluorescent virus-like-particles and on non infectious labelled virus expressing host cells with labelled actin or tubulin cytoskeleton nano-filaments in fixed and living host cells. The workshop will have 3 parts: Part 1: presentation of the microscopie STED principle (J.Swain, IRIM , CNRS Montpellier) and of the virological system for STED imaging (D.Muriaux, IRIM CNRS Montpellier) Part 2: image acquisition of fixed virus and infected cells labelled for 2D and 3D imaging + explanation for sample preparation (J.Swain/D.Muriaux) and virus size analysis on the microscope computer (comparing Confocal versus STED resolution in xyz) and using imagJ (show on a laptop during the workshop) Part 3: Preparation of live cells expressing fluorescent virus-like particles (labelled with eGFP) with a live staining for F-actin or Tubulin and movie acquisitions with live STED 2 colors (D.Muriaux/J.Swain)