Abstract: Adult neurogenesis is a highly dynamic process that leads to the production of new neurons from a population of quiescent neural stem cells (NSCs). In response to specific endogenous and/or external stimuli, NSCs enter a state of mitotic activation, initiating proliferation and differentiation pathways. Throughout this process, NSCs give rise to neural progenitors, which undergo multiple replicative and differentiative steps, each governed by precise molecular pathways that coordinate cellular changes and signals from the surrounding neurogenic niche. The ultimate goal of this complex genetic machinery is to ensure a continuous supply of new mature and functionally active neurons to pre-existing neural circuits, while also maintaining the neural stem cell pool as intact as possible, both under physiological conditions and in response to positive or negative external stimuli (Niklison-Chirou et al., 2020). In fact, disruption of this delicate balance can lead to neurogenic deficits or depletion of the NSCs pool. In this context, p21 has been identified as a key regulator of two pivotal processes in adult neurogenesis: the transition between quiescence and activation of NSCs, and the progression of progenitor proliferation (Maeda et al. 2023).