How do we choose a mate? What is love all about? Why does opposites attract? Scientists have been trying to uncover the mysteries. So far, they have calculated the shape and angles of human face, researched the symmetry of dancers' body, listed out the "attraction" equation by measuring the bodies of Playboy models, and listed out the qualities and personalities that attract both men and women. Although there are still many unknown areas, the checklist of scientific rules of the game of love is emerging.