2. Huangdi Neijing is one of the four classic works of traditional medicine in China and the earliest medical classic in China. It is a medical masterpiece that studies human physiology, pathology, diagnostics and pharmacology. Theoretically, the theories of yin and yang, five elements, pulse condition, Tibetan image, meridians, etiology and pathogenesis, disease, diagnosis, health preservation and luck are established. His medical theory is based on China's ancient Taoist theory, which embodies China's ancient thought of harmony between man and nature.