There are five organ networks: Metal, Water, Wood, Fire, and Earth. Each is associated with its own meridian and set of functions.
Water network (水行): the kidney meridian (腎経)
The kidney consolidates and stores the Ki that initiates and keeps life growing. Like a minister of the interior who conserves natural resources, stockpiling essential raw materials for use in time of growth, crisis, or transition, the kidney preserves what is essential, essential to human life. It is a well of vitality and endurance. Kidney contains the germ of intellect and creativity and houses our instinct to procreate and survive.