Similar to the yin yang theory, the five elements theory also originated from the observation and sense of the universe. Ancient Chinese people believed that the universe consist of five basic elements, i.e., Metal, Water, Wood, Fire and Earth (Soil). Everything in the universe, including the human being, must have a relationship with the five elements. They applied the five elements not only to every physical object in the world, but also to Colors, Directions, Seasons and Sounds. According to the theory, the elements are moving, waning, waxing and changing all the time. Their interdependence and interaction explain the complex connections between objects, between the human body and the natural world, and between organs inside the human body. Like Yin and Yang, interactions of five elements are slow and stable when they are in balance. If they are out of balance, interactions become unstable and unpredictable. Individuals will be sick then.

The following table shows the objects classification according to the five elements:

The relationships and interactions among five elements are explained below:

Water can help tree (Wood) to grow. Wood can help Fire to burn. Fire can help to produce dust (Earth). Earth can help mineral (Metal) to form. Metal can hold Water.

On the other side, Water can extinguish Fire, Fire can evaporate Water. Wood can break the ground (Earth), Earth can bury Wood. Fire can melt Metal, Metal may not melt before Fire is extinguished. Earth can absorb Water, Water can cover the land (Earth). Metal can cut Wood, Wood can dull the Metal.

In TCM, the visceral organs, as well as other organs and tissues, have similar properties to the five elements: they interact physiologically and pathologically. The Five Elements theory is utilized to explain the correlation between internal organs, their pathological effects on each other, and corresponding medical diagnosis and treatments. For example, kidney (water) stores essence. Liver (wood) holds blood. The essence in kidney nurtures the blood in liver. In other words, the water of kidney feeds the wood of liver. This explains that water produces wood in a human body. Liver (wood) stores blood. Heart (fire) controls the blood circulation. The blood in liver helps adjust the quantity of the blood circulation and assists heart to function normal. In other words, the wood of liver nourishes the fire of heart. This is another example that wood breeds fire in a human body.

When these changes are stable and balanced, an individual is healthy. If the balance is broken, the individual will be in bad condition and illness comes after. The herbal treatment can be prescribed according to the problem and Five Taste characteristics.