The wu xing (wood, fire, earth, metal and water), are the five phases of Chinese cosmology, better understood as processes or agents than as static substances. They stand in two principal cycles: the generating cycle, in which each produces the next (wood feeds fire, fire makes ash and so earth, earth bears metal, metal carries water, water nourishes wood), and the overcoming cycle, in which each controls another.
The five phases are one of the great organising schemes of Chinese thought, sorting seasons, directions, colours, organs, emotions, flavours and much else into five correspondences, and running through medicine, divination, feng shui and statecraft.