The theory of five elements explains how Qi (all the vital substances) cycles through various stages of transformation. As yin and yang continuously adjust to one another and transform into one another in a never-ending dance of harmonization, they tend to do so in a predictable pattern.
In both Chinese philosophy and medicine, these stages of yin-yang transformation are referred to as the wu xing, the "five phases of transformation." They are listed below.
lists of correlations for the five elements are endless, but they do
follow a certain simple logic that many people find makes intuitive
sense. For example, each phase of transformation gives birth to, and
nourishes, the next phase in sequence ( i.e. water nourishes wood, wood
nourishes fire, etc.).
Each phase of transformation also has a restraining influence on the phase opposite to it (i.e. water restrains fire, wood restrains earth, etc.). By increasing or decreasing the qualities and functions associated with a particular phase, a practitioner may either nourish a phase that is in deficiency or drain a phase that is in excess or restrain a phase that is exerting too much influence.
for some reason, there is disruption in the smooth transformation of
yin and yang at any phase of the cycle, then the resulting disharmony
can manifest itself in a number of qualities corresponding to that
phase. Thus the principle of the Five Phases of Transformation can be
used for diagnostic purposes and also for creating strategies of
intervention to address the disharmony.
This is an ancient theory that still has many applications in TCM, especially in Chinese herbal and dietary therapies.