The human brain is the most complex structure in the known universe. Learning how it works, the relationship between mind and brain, is one of the most fundamental and important of scientific questions and neurobiology one of the fastest growing research areas. New tools, from molecular genetics to the windows into the brain offered by imaging techniques, have transformed our understanding. Brain researchers now claim to be able to explain the roots of human personality and behaviour, of language and even of consciousness itself.Coupled with claims of new knowledge come potential new powers, to cure devastating diseases like Alzheimer's, to control behaviour through tailor-made drugs, to develop human-machine hybrids - cyborgs. But just how far have the neurosciences come in their claims to be able to understand mind and brain? How seriously should we take these new threats and promises?