The sea of qi refers to danzhong where pectoral qi concentrates and originates. Danzhong refers to the central part of the chest where the lung is located, promoting breathing and governing the qi flow in the entire body. The lung, connecting all the vessels and meridians, can distribute the nutrients of food and drinks to replenish and nourish the entire body. Danzhong is the “sea of qi” where pectoral qi converges. It is alternatively named the “upper sea of qi.” The “sea of qi” is also the name of an acupoint located in the middle of the abdominal midline, i.e., the upper sea of qi. It is indicated for collapse, syncope, abdominal pain, diarrhea, irregular menstruation, dysmenorrhea, uterine bleeding, leucorrhea, seminal emission, impotence, enuresis, and hernia.