Yin-Yang

What you see above is a Yin-Yang symbol. Along with the peace sign and the symbol of the cross, it has become a popular ornament today. It can be found in most pop jewelry stores. It can be worn around one's neck, on one's ears, or even as a pendant on his clothing. One can sew it on his pants, or buy a shirt with the symbol already on it. The more daring might even choose to have it tattooed on their bodies. What is this symbol? Where did it come from? What does it mean? Or, are these...