The nervous system has a remarkable capacity for self-reorganization, and in this first systematic analysis of the interaction between hormones and brain plasticity, Luis Miguel Garcia-Segura proposes that hormones modulate metaplasticity in the brain. He covers a wide variety of hormones, brain regions, and neuroplastic events, and also provides a new theoretical background with which to interpret the interaction of hormones and brain remodeling throughout the entire life of the organism.