This is the basis of good health and as such is maintained by the Vita-vapor, which is both physical and moral. The movement of Tao gives rise to vita-vapor. The spontaneity of vita-vapor gives rise to yin and yang interactions. Yin and yang are the opposite expressions of the same reality. Mass and energy are the opposite expressions of the same vita-vapor.
Energy is represented by yang and mass by yin.
The union of yin and yang becomes harmony. This union of harmony is possible because they are opposite. It is because they are opposite that interactions take place. This is the source of interactions. Yin and yang concept is applied to all opposites in the universe, to substance and to motion.