This review traces the history of neuroscience from its origins to recent times. Early physicians recognized that the brain controls sensation and movement, learning and thought, and that communication between the brain and the body is by way of the spinal cord. A fundamental principle of nervous system structure is the neuron doctrine, the idea that brain and spinal cord are made up of individual elements called neurons, which may touch one another but do not fuse. Communication among neurons and activation of muscles is accomplished in most cases by release of a chemical transmitter substance. Understanding of the nature of electrical signalling in the nervous system culminated in the discovery of the ionic basis of the action potential. Early observations of the effect of brain injury on speech and language, sensation and movement revealed that different parts of the brain and spinal cord are specialized for different functions. The development of techniques for single-cell recording in animals and computer-based imaging in humans showed that there are multiple cortical areas dedicated to further processing of the sensory message, and control of movement.