Five Elements
According to ancient Chinese people, the world is made up of five elements: Metal, Wood, Water, Fire and Earth. It may look a bit similar to the ancient Greek concept of four elements, i.e., Water, Fire, Air and Earth. I’m not too familiar with the Greek concept, but I know the Chinese one is not as simple as it may look like. It is a complicatedly intervening living system. It forms the foundation of many Chinese philosophical thoughts and is crucial in understanding Chinese traditional culture.
On the one hand, the five elements are mutually dependent. Metal gives rise to Water. Water gives rise to Wood. Wood gives rise to Fire. Fire gives rise to Earth. Earth gives rise to Water. That is a circle.
On the other hand, the fire elements also suppress each other. Metal suppresses Wood. Wood suppresses Earth. Earth suppresses Water. Water suppresses Fire. Fire suppress Metal. That is also a circle.
Their relations are shown in the figure below.

Some of the relations are very obvious, such as “Water suppresses Fire” and “Wood gives rise to Fire”. Others may seem not so easy to understand. Just remember that these elements do not only refer to concrete materials. They are abstract concepts, or the Five Motions. For instance, Metal also stands for autumn and west. When autumn comes and west wind begins to blow, trees will wither. No wonder why Metal suppresses Wood.
Use your imagination and try to explain the nature with this theory.