五行思想
In many traditional Chinese theory field, matters and its developmental movement stage can be classified into the Wu Xing. They are Wood ruler Jupiter, Green, East and Spring, Fire ruler Mars, Red, South and Summer, Earth ruler Saturn, Yellow, Center and Last Summer, Metal ruler Venus, White, West and Autumn and Water ruler Mercury, Black, North and Winter. Note that the Wu Xing are chiefly an ancient mnemonic device for systems with 5 stages, rather than the notion of different kinds of material.