body. Congenital and acquired jing have a promoting/ controlling relationship with each other and their interaction produces kidney jing; all three play a part in determining growth and development, sexual maturation, reproduction, and aging. Every new jing cycle prompts a new cycle of development. For example, congenital jing exists from conception, carrying on from the jing of the parents. Once a child is born, acquired jing is responsible for replenishing congenital jing and starting the first independent jing cycle which, for the next seven years in girls and eight years in boys, will control growth and development. When the child loses its baby teeth, its body begins the pre-adolescence cycle. The next jing cycle is adolescence, when kidney jing matures and causes the ren meridian to open and flow. At this time, part of the kidney jing transforms into tian gui, which develops and maintains reproductive function. In the next stage physical growth finishes, and eventually declining jing leads to exhaustion of tian gui, thus extinguishing reproductive ability. Inevitably, decline of jing leads to death. Energy aspects All of the four kidney energy aspects are essential in growth and development. These four aspects include kidney jing (essence), kidney yin (water), kidney yang (fire) and kidney qi. All of the body's functions rely on the heat provided by kidney qi and the gate of life (the space between the left and right kidneys). Kidney jing is the foundation of the yin and yang of all the body's organs. Kidney yin and yang are the primordial yin and yang, and the root of yin and yang to the zang organs. Kidney yin moistens and nourishes, while kidney yang provides warmth and promotes organs and tissue. kidney yang is the dynamic force necessary to start the system of balancing water metabolism, which also employs the spleen, lung, liver and san jiao. Dominating water metabolism The kidney is considered a water element. As the body's water gate, it regulates water metabolism and reception of qi. The foundation of yin fluid that nourishes and moistens the body is kidney yin. When the kidney receives fluid the qi of kidney yang divides it into two types, clear and turbid. Clear fluid is sent upward through San Jiao to moisten the lung and for the lung to distribute to the body, while turbid fluid is sent downward for expulsion by the bladder. The water gate is also