"The Divine Peasant's Herbal" has been reputed to be one of the first known books and has been estimated to appear around 200 B.C.  Also about that time "The Yellow Emperor's Classic of Medicine (Huang Di Nei Jing)" appeared.  The "Nie Jing", as it is most commonly known, is the book in which much of modern Traditional Chinese Medicine is based. 

The book "Discussion of Cold Induced Disorders" (Shang Han Lun) by Dr. Chang, appeared about 400 years later, in 219 A.D.  This text demonstrates the sophistication of Chinese Herbal Medicine in that it has survived, almost seventeen centuries later, in which the original prescriptions are still used today throughout the clinics and hospitals of China.  This text remains today as a main source on which Chinese Herbal Medicine is based.

Over the last 2000 years, herbs began to be applied in complex combinations to treat specific ailments.  These combinations - called formulas - are a living body of knowledge, always building on thousands of years of practical experience.  In pill form, these classic and traditional formulas are called "patent formulas."