According to Chinese cosmology, the universe is composed of two opposite and complementary principles which are in constant interaction and balance. Yin represents the feminine, passive, dark, and cool aspects of nature. Yang represents the masculine, active, bright, and warm aspects of nature.

Yin is considered to be the complementary opposite of Yang, which represents active, masculine, and warm energy. Together, Yin and Yang are believed to be the two fundamental forces that create and balance the universe.