The kidney is located at the waist, one on the left and one on the right, with the lower right side and the upper left side, and its shape is elliptical and curved, like cowpea. Kidney governs storing essence, growth and reproduction, water and qi. It is the source of yin and yang of human viscera and the source of life, so it is called the innate source. If you are overworked and lustful, or if you have been ill for a long time, you are prone to kidney deficiency.