Pop quiz: just how important is the brain? Ascribing the formulation and control of thoughts and feelings to the heart, and calling the brain "an organ of minor importance," was just one of a surprisingly high number of ludicrous assertions made by Aristotle. In the modern day, some 2,500 or so years later, we appreciate the importance of the brain, though we may not be very much closer to truly understanding it. As the author Isaac Asimov once said, the human brain is "the most complicated organization of matter that we know".
But we do know more now than Aristotle did. We understand the physiology of the brain, its central role in our lives, and how and why it acts—or causes us to act—in certain ways. So, here's an introduction to what we do know about a subject as fascinating, complex, and full of twists and turns as... well, the brain itself.