Figuring out how the heart functions in a metaphorical sense can be an unending and highly metaphysical process (just ask John Donne), so it's nice to find a place online where visitors can learn how the heart functions in a literal sense. This website was created by the National Heart Lung and Blood Institute, and begins by answering the basic question: "What is the Heart?" After reading this short and informative piece of writing, visitors can meander through sections titled "Anatomy", "Contraction", "Circulation", "Electrical System", and "Heart Disease". Each section provides a brief summary of each topic, complete with graphic illustrations and several digital animations. It's a well-constructed and user-friendly introduction to this important topic, and one that will be of use to those entering one of the health care professions, or those who are intrigued with various body systems.