For most biological questions, it is essential to monitor in vivo and in real time the complex cellular machinery with extreme sensitivity and ultimate resolution. The fluorescence thus remains the tool of choice for specific monitoring in biology. Beyond imaging intensity to a specific location, fluorescence and its various spectroscopic properties can be used to locally probe its environment or reveal interactions. The photophysical properties of fluorophores are the basis of recent developments, which have enabled microscopy to turn into nanoscopy, exceeding the resolution limit imposed by diffraction, enabling the detection of single molecules with nanometer resolution. This level of resolution allows to consider the study of biological systems at a scale unprecedented in optical microscopy. The developments of the team aim to correlate functional and structural 3D information in different biological applications. In particular we develop different strategies to take advantage of supercritical angle fluorescence (SAF) emission.