On March 15, 1901, Henri B enard defended his thesis entitled "Les Tourbillons cellulaires dans une nappe liquide propageant de la chaleur par convection en 1 r egime permanent" at the University of Paris, Sorbonne. The results contained in this thesis have been at the origin of recent intensive research activities on c- lular structures observed in many physicochemical systems far from equilibrium: instabilities, spatio-temporal patterns, chaos, and turbulence. The French Physical Society organized a scienti?c meeting to commemorate the centenary of B enard's thesis, at the Ecole Sup erieure...