How does the brain produce a thought? Or experience a unitary, whole, synchronized perception of a cup of coffee? For neuroscientists, this is the Mount Everest of questions. We have a look at one possible theory (that a thought is like lots of little neurons singing together in harmony) and then visit neurologist Christof Koch to ask: who conducts the brain chorus? Koch thinks he knows, and he tells us of the cutting edge work of one of science’s great thinkers, Francis Crick...an inquiry which lasted until his dying day.