The book “Cerebro y ejercicio” (“Brain and exercise”) is a new volume in the CSIC collection “¿Qué sabemos de…?” (”What do we know about…?”). This is addressed at a wide reader audience to bring the latest advances in the knowledge of the beneficial effects of physical exercise for the correct functioning of the brain. Both mechanisms studied, in the laboratory in animal models and the known effects on the human brain, are discussed. Its authors are the neuroscientists José Luis Trejo of the Cajal Institute of Madrid (IC) and president of the Consejo Español del Cerebro (Spanish Brain Council) and Coral Sanfeliu of the Institute of Biomedical Research of Barcelona (IIBB) and of the CIBER of Epidemiology and Public Health. The first chapter introduces the concepts of types of exercises and the effects on the body. It follows a block of three chapters where the concept of the hormesis effect and the neurobiological mechanisms involved in physical exercise are presented from the molecular level to the integral level that gives the behavior. In the next block of three chapters, the effects derived from the practice and physical activity of daily life on the modulation of the brain are presented, emphasizing the benefits against brain aging and associated diseases. The book closes with a final note, a glossary of technical terminology and abundant scientific bibliography that will be of interest to interested scientists to delve into the subject. Together we want to convey the great impact that physical exercise has on multiple aspects of the brain and its potential as a non-pharmacological therapy and perhaps soon against depression, cognitive decline with age and neurodegeneration.