Understanding the brain and how it functions has been a core scientific endeavour ever since its role in sensory and cognitive functions was first identified. Groundbreaking work in the nineteenth and twentieth centuries, such as the first recording of electrical brain activity (Caton, 1875), the discovery that neurons are the discrete units of the nervous system (Ramón y Cajal, 1894), and the functional mapping of the cortex (Penfield and Rasmussen, 1950), has laid the foundation for investigating how human health relates to brain anatomy and function. Since then, the neurophysiological underpinnings of various phenomena such as sleep, consciousness and cognition have been studied. Pathologies that originate in the brain, such as epilepsy, dementia, and sleep disorders, are also the subject of ongoing research. Ultimately, a better understanding of how the brain works could help prevent, treat or manage diseases, and even identify ways to optimize its overall performance.