The purpose of my PhD thesis is to contribute to the characterization of the immediate signaling events that trigger cellular remodeling processes in an organism undergoing regeneration. The laboratory of Prof. Brigitte Galliot uses the cnidarian Hydra, one of the ‘oldest' known model system, to study regeneration. Indeed, advances in the field of Hydra regeneration contribute to a comprehensive knowledge of regenerative mechanisms across the animal kingdom. We present three questions addressed in this thesis, aimed at deepening our understanding of the amazing regenerative ability in Hydra: 1) Which immediate injury-induced signal promotes regeneration in Hydra? 2) More specifically, what are the injury-induced signals that promote MAPK activation and regenerative cell death? 3) How do injury-induced signals contribute to the reactivation of developmental programs?