The book explains how to understand cognition in terms of brain anatomy, physiology and chemistry, using an approach adapted from techniques for understanding complex electronic systems. These techniques create hierarchies of information process based descriptions on different levels of detail, where higher levels contain less information and can therefore describe complete cognitive phenomena, but are more approximate. The nature of the approximations are well understood, and more approximate higher level descriptions can therefore be mapped to more precise detailed descriptions of any part of a phenomenon as required. Cognitive phenomena, the anatomy and connectivity of major brain structures, neuron physiology, and cellular chemistry are reviewed. Various cognitive tasks are described in terms of information processes performed by different major anatomical structures. These higher level descriptions are selectively mapped to more detailed physiological and chemical levels.