We are in the midst of a revolution. For centuries science has made great strides in our understanding of the external observable world. Physics revealed the motion of the planets, chemistry discovered the fundamental elements of matter, biology has told us how to understand and treat disease. But during much of this time, there were still many unanswered questions about something perhaps even more important to us. That something is the human mind. What makes mind so difficult to study is that, unlike the phenomena described above, it is not something we can easily observe, measure, or manipulate. In addition, the mind is the most complex entity in the known universe. To give you a sense of this complexity consider the following. The human brain is estimated to contain ten billion to one hundred billion individual nerve cells or neurons. Each of these neurons can have as many as ten thousand connections to other neurons. This vast web is the basis of mind, and gives rise to all of the equally amazing and difficult-to-understand mental phenomena such as perception, memory, and language.