Until recently, theories of the brain and its diseases, and how it gives rise to mind and emotions were based on the model of a static, non-renewable network of nerve cells and their connections. Then, seemingly overnight, a revolutionary new conception of the brain emerged in the mid-1990s. The sudden convergence of discoveries that had been building over decades led to the revelation that, far from being an immutable black box, the brain is a plastic, ever-changing marvel, no less dynamic than our thoughts and emotions—a complex system that is continually shaped and reshaped by a subtle interplay of genetic cues and life experiences.