Why are most living creatures condemned to die "naturally" even when they have a favourable and protected environment? Is death a "useful" biological process or does it not correspond to any natural necessity? Biology has only recently begun to address these issues. However, today it provides a coherent and rigorous framework for interpreting death, its existence as mechanisms at the very heart of life. André Klarsfeld and Frédéric Revah take stock of all this research, which overturns many preconceived ideas on a subject that has haunted humanity since the beginning. André Klarsfeld is a neurobiologist and researcher at the Alfred-Fessard Institute of the CNRS in Gif-sur-Yvette. Frédéric Revah is a neurobiologist by training. He was a member of the Institut Pasteur and held positions of responsibility in the pharmaceutical industry. He is now a scientific director in a biotechnology company.