The “bible” of TCM. This book is over 2000 years old, and was supposedly written by the legendary “Yellow Emperor,” Huang Di. Because of this, it is often referred to as the Huang Di Nei Jing. The Nei Jing discusses Yin/Yang theory and Five Elements theory as they apply to the human body; Zang Fu theory, tongue diagnosis, pulse diagnosis, meridian theory, disease processes, and acupuncture techniques, among other subjects (the italicized terms are defined in more detail individually in the Glossary).