Sun Si-miao was a renowned physician during the T'ang Dynasty, and completed the Invaluable Prescriptions for Ready Reference around 652 AD. The book contained chapters on gynecology, pediatrics, internal, external and the facial features, totaling 232 sections with more than 5,300 prescriptions, and is the oldest surviving medical encyclopedia today. In his later years he further wrote a Supplement to Invaluable Prescriptions for Ready Reference. He particularly emphasized the importance of medical ethics, and believed that a physician must possess not only professional knowledge but also a truly compassionate heart, treating all patients equally. !