Biological systems propose new challenges and offer a wide spectrum of behaviors, all being sources of inspiration for physicists. The complexity of their organization can be observed from the nanometric scale (proteins and macromolecules) or the microscopic scale (living cells), to the macroscopic scale (organs and living organisms). The studies carried out in this group aim at understanding the structure of this multi-scale and multi-functional organization, and in particular at identifying the role played by geometric complexity in the working of living systems. The topics covered are :