The human brain is the most complex structure in the known universe. How it works, the relationship between mind and brain is one of the most important of scientific questions. Researchers now claim to be able to explain the roots of human personality and behaviour, and this new knowledge brings potential new powers: to cure mental illnesses, to control behaviour through tailor-made drugs, to develop human-machine hybrids. But just how seriously should we take these new threats and promises? In order to tackle these issues Steven Rose explores the evolutionary routs by which brains emerged, from the origin of life to today's complex societies. He also investigates how brains develop from a single fertilised egg to the incredibly complex organ that each human possesses. Against the background he asks the challenging question: what does the future hold for the human brain?