This book reflects two symposia held in Geneva in autumn 1995. The first, on "Integration of Plants, AnimaIs and Man, in Time", was held under the auspices of CLUSE, an association of the French Universities of Besançon (Franche-Comté) and Dijon (Bourgogne) and the Swiss Universities of Berne, Fribourg, Lausanne, Neuchâtel and Genève. The other meeting, on the "Foundations of Biological Rhythms", was supported by the Third Cycle of Studies in Biology combining the above mentioned Universities from Switzerland. Sixteen speakers from France, England, Germany and Switzerland developed topics on biorhythmicity covered under the following key-words: physico-chemistry, genetics, signaling, and clock-controlled integration of growth and differentiation.