Our hearts have evolved to be extremely efficient, long-lasting pumps that exquisitely match the needs of our bodies. This book is about how the heart does this; how can a heart pump the blood for up to 100 years while the best Formula 1 racing engine has a working life measured in hours? Why is the heart so efficient, and how are worn out parts replaced while working? How does it generate the force to act as a pump, how is it controlled electrically, and how can it repair itself? This book addresses these questions from physiological and molecular perspectives in language that aims to be accessible to all interested in biology and with liberal illustrations. The story of how the heart works is presented in the context of its origins:How is the heart formed in the womb? How it evolved as an oxygen pump through many configurations following the onset of oxygenic photosynthesis 2.5 billion years ago? Why its intimate co-evolution with the circulation and blood was essential to enable its efficiency and longevity? The book begins with a discussion of why the word heart is universally used as a metaphor for reason and emotion and traces its origins in modern and ancient languages. The last chapter offers advice on how to preserve the heart by matching our lifestyles more closely to how it evolved.