In Chinese creative theory, the universe develops out of a primary chaos of primordial qi or material energy, organized into the cycles of yin and yang, force and motion leading to form and matter. “Yin” is retractive, passive, contractive and receptive in nature in a contrasting relationship to “yang” is repelling, active, expansive and repulsive in principle; this dichotomy in some form, is seen in all things in nature and their patterns of change, difference and transformations. For example, biological, psychological and cosmological seasonal cycles, the historical evolution of landscapes over days, weeks, years to eons.
― Yin and yang Wikipedia page
