Here is the essential guide to the human brain, an authoritative reference book and timeline that examines the three pounds of matter inside our heads that does all our thinking for us. The human brain has 100 billion nerve cells connected by thousands more to every corner of the body. The brain s cells are wired together with 100 trillion connections. That makes each and every human brain a contender as the most complex system in the universe, a system that endows us with an intellect that far outstrips that of any other creature. However, there is one difficult question remaining: Are we intelligent enough to understand our own brains? Follow the journey as history s greatest brains, such as Avicenna, Thomas Willis, Charles Darwin, and Paul Broca, try to figure it out by linking the structure of the brain to its functions. How does the brain control the body, how does it make sense of our surroundings, and allow us to understand, empathise with and love other people (and their brains)? And how does it create that most mysterious feature of the universe consciousness.