"We are at the end of our extensive journey into the heart of matter. It has been marked as a relentless march toward Unity. As physics progressed, intimate connections were discovered between phenomena once thought to be completely distinct. A unified description of Nature, sometimes referred to a bit pompously as "the theory of everything," has become the holy grail of modern physics. Symmetry has constantly and reliably guided the physicists' first hesitant steps in this quest for Unity. ...becoming increasingly abstract. ...Now scientists routinely deal with "matter-light symmetry.""