This book is the result of the second seminary concerning theoretical biology that was organized at Geneva for the Third Cycle of Studies in Biology, grouping students from the following universities Berne, Fribourg, Lausanne, Neuchâtel and Genève. The proposed topics by the 15 invited speakers from France, Germany and Switzerland were: system analysis, dynamic systems, thermodynamics, energetics, auto-organization, physico-chemistry of systems out of equilibrium, chronobiology, glycolytic oscillations, ion fluxes in evolving cell, oscillation and communication, mechano-chemical growth, fractals and senescence.