Tens of millions of households in the United States have pets. They are often considered integral parts of families and close companions. There is a long history of domesticating animals, and this volume in part considers the intertwined evolution of animals and domestic animals to examine how these relationships have developed. It discusses the characteristics and behaviors of cats, dogs, and other animals that allows humans to create such a strong bond with them. It also looks at recent research on the advantages pets have on physical and mental health.