Ancestral energy (Qi of the chest) is needed to form the Qi that is transformed from food and air. In the Middle Warmer, essential energy (zong Qi) is "cooked" from food and air. Qi; the Middle Warmer is the stove and the ancestral energy is the fuel. The zong Qi moves up to the chest, nourishes the Heart and Lung to promote their functions, and divides into yong Qi and wei Qi. Yong Qi is nutrient Qi; its function is to nourish the body and maintain its substance. Wei Qi is defensive energy that defends the organism against exogenous pathogenic influences.