<i>De Rerum Natura</i> : How Do Halide Perovskites Self‐Heal From Damage?

By actually addressing the title question, we provide a comprehensive and critical review of self-healing (SH) in lead-based halide perovskites (HaPs), a phenomenon with profound implications for the stability of these materials across all applications, from photovoltaics to light emission and radiation detection. We emphasize reasoning as a guide to interpreting the dynamic balance between degradation and recovery when HaPs are exposed to light, heat, mechanical stress, or radiation. We compile and assess what are, in our view, the most relevant, available reports of damage-healing dynamics, distinguishing verified facts and observations from interpretations and unresolved questions. Key topics include damage accumulation, light soaking, and photo-brightening, as well as the mechanistic roles of lattice dynamics, halide migration, redox chemistry, and acid-base equilibria in the disappearance of defects on accessible time scales. Thus, we go beyond a conventional summary by providing a unifying framework to clarify contradictions in the literature and reveal the underlying principles of reversible damage. By consolidating results that are often scattered into a coherent picture, we strive to establish a foundation for predictive models of SH kinetics, while guiding strategies to stabilize devices. We anticipate that this critical synthesis will serve as an authoritative reference for the metal halide perovskite research field.