Yin and yang
In Ancient Chinese philosophy, yin and yang is a concept of dualism, describing how seemingly opposite or contrary forces may actually be complementary, interconnected, and interdependent in the natural world, and how they may give rise to each other as they interrelate to one another. In Chinese cosmology, the universe creates itself out of a primary chaos of material energy, organized into the cycles of Yin and Yang and formed into objects and lives. Yin is the receptive and Yang the active principle, seen in all forms of change and difference such as the annual cycle, the landscape, sexual coupling, the formation of both men and women as characters and sociopolitical history.
Read article on Wikipedia