Here´s another Yin Yang related pic. I mentioned the concept before. For those who haven´t read that post, here you go:
The concepts of yin and yang originate in ancient Chinese philosophy and metaphysics, which describe two primal opposing but complementary principles said to be found in all objects and processes in the universe.
Yin (Chinese: 陰 or 阴) is the darker element; it is passive, dark, feminine, downward-seeking, and corresponds to the night.
Yang (陽 or 阳) is the brighter element; it is active, light, masculine, upward-seeking and corresponds to the day.
Yin is often symbolized by water or earth, while yang is symbolized by fire, or wind.
Yin and yang are descriptions of complementary opposites rather than absolutes. Any yin/yang dichotomy can be seen as its opposite when viewed from another perspective. The categorization is seen as one of convenience. Most forces in nature can be seen as having yin and yang states, and the two are usually in movement rather than held in absolute stasis.