Whereas other fields continue to become more complex and specialized, physiology happily remains an area that can still be understood by thinking from first principles. However, given the increasing quantity of information available today, it is easy to become overly concerned with details and give in to the temptation to memorize rather than understand. In this concise book, the authors convey their enthusiasm for physiology and convincingly persuade the reader that with a sound understanding of principles, details often fall effortlessly into place. It is by no means an attempt to produce another comprehensive textbook. Instead, a broad overview of the subject is presented, covering areas that are not given the attention they deserve in other texts whilst purposely omitting those aspects where memorization is an unfortunate necessity.