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 de Physique et Chimie Industrielles de Paris (ESPCI). This meeting, which gathered approximately one hundred scientists and graduate students working in nonlinear science, was honored by the presence of the director of the ESPCI, Professor Pierre-Gilles de Gennes, Nobel laureate in physics (1991), who gave the opening talk. At the conference, lectures were given by internationally recognized scholars who have contributed to the development of B' enard's work: J.E. Wesfreid, P. Manneville,Y.Pomeau,M.Velarde,J.Gollub,M.Provansal,G.Nicolis,B.C- taing,andP.Coullet.Apostersessionandaroundtableonfurtherdevelopments in nonlinear physics were organized. In the present book, we have extended the list of contributors in order to cover all the aspects involved with B' enard's work, with a main focus on th- mal convection, on B' enard-Marangoni instability and on B' enard-von Karman instability. WewouldliketothankDr.HansKoelschfromSpringerforthepublicationof this monography in the Springer Tracts in Modern Physics series. We ackno- edge a critical reading by C.D. Mitescu and a very helpful technical assistance from Olivier Crumeyrolle.