Just as we were getting a grasp on the human genome, with all of its warts, mutations, and instability—along comes another concept to keep us captivated with the scientific (and financial) literature for years to come. This chapter in the post-Darwinian synthesis is of sufficient import to be labeled the "Breakthrough of the Year" by Science magazine.1 One can also be assured of interest after the wide dissemination in the lay press.2