Please look at the center for the Taiji or Yin and Yang design.
The Yin and Yang or Taiji (Tae-Kieh as it is called in some old sources) is a Taoist symbol of the dichotomy of duality in nature. Light and dark, male and female and so on are represented in the Yen and Yang. Notice in the common representation there is a circle of the other in each side.
The Art Institute of Chicago divides them as such:
The Five Phases
greater yang: wood and spring (east)
lesser yang: fire and summer (south)
greater yin: metal and autumn (west)
lesser yin: water and winter (north)
the central phase: earth and the solstices