Lung qi, the essential qi of the lung, is the material basis and driving force of the physiological activities of the lung. Lung qi is the qi and essence in the whole body distributed to the lung to perform special functions. It has a prenatal source and a postnatal source. Prenatally, lung qi is rooted in the original qi in the kidney, which is transported upward to the lung via triple energizer (sanjiao) and becomes part of lung qi. Postnatally, lung qi comes from pectoral qi transformed from nutrients of food and drinks ingested and fresh air inhaled. Via its functions of dispersion, depuration, and descent, lung qi governs respiration, regulates body fluid metabolism, and assists the heart in promoting blood circulation.