Besides its function as a passive cell wall plasma membrane (PM), involved in signal transduction and cell adhesion, is essential to enable the formation of tissues. Understanding PM function requires molecular insights into its dynamic spatial organization. Recent studies show that membrane proteins rearrange laterally forming nanoclusters of various size. On the other hand, a hierarchical model of two dimensional PM organization has been proposed including transient confinement in membrane-actin-skeleton induced compartments and lipid rafts. However, an overall picture of the dynamic spatial organization of the PM requires the inclusion of protein trafficking since membrane proteins undergo a constitutive turnover transported in vesicles as cargo from and to the cytosol.The hypothesis of this project is that vesicle trafficking to and from the PM is responsible for the observation of nanoclusters in the PM. Due to the diffraction barrier it is impossible to image nanoclusters with conventional fluorescence microscopy. To avoid this limitation, I will use super-resolution fluorescence imaging methods such as direct Stochastic Optical Reconstruction Microscopy (dSTORM) and Photoactivated Localization Microscopy (PALM) combined with novel statistical cluster analysis to study quantitatively the dynamic reorganization of PM induced by protein trafficking, as well as the role played by actin-skeleton-induced compartments and lipid rafts during this process. I will apply this approach to study a wide family of membrane proteins involved in signal transduction and cell adhesion essential for embryogenesis, neurogenesis, and immune response. The outcome of the project is expected to provide fundamental new insights into PM architecture and organization including protein turnover. Since membrane proteins are one of the most attractive drug targets because they control the communication of cells with their environment, the results will be of high medical significance.