
The curves and circles of the Yin-Yang symbol imply movement represents the ways in which Yin and Yang are mutually-arising, interdependent, and continuously transforming, one into the other. One could not exist without the other, for each contains the essence of the other (represented by the smaller circles nested within each half of the symbol) .
taken from: http://taoism.about.com/od/visualsymbols/ig/Taoist-Symbols/Yin-Yang-Symbol.--jj.htm

Dance of opposites. Nice :)