The curves and circles of the Yin-Yang symbol imply a kaleidoscope-like movement. This implied 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. Night becomes day, and day becomes night. Birth becomes death, and death becomes birth (think: composting). Friends become enemies, and enemies become friends. Such is the nature - Taoism teaches - of everything in the relative world.