Our group aims at deciphering the interplay of physical and biological mechanisms that underlie the establishment and maintenance of the multiscale architecture of living cells. To this end, it is critical to analyze at a molecular scale the mobility of proteins and to properly account for the stochastic mechanisms that govern the behavior of individual molecules. Yet, it must be also recognized that the transfer of information, from the molecular to the cellular scale, is mediated by networks of interactions whose dynamics and organization need to be described and are largely influenced by properties of their individual molecular constituents. In this context, our team develops imaging assays using two complimentary approaches: (1) with single molecule imaging tools, we are probing the structural, stoechiometric and dynamic properties of macromolecular assemblies in live cells, (2) with optogenetic or magnetic manipulation, we are studying the cell response to controlled perturbations, in order to decipher the molecular circuits underlying information processing and decision-making events at the single cell level. We are currently applying these tools to the study of the formation of cell polarity during migration and division.