People have always asked what distinguishes the living from the inanimate world and what uni?es the two. The ?elds of biology and physics have a long history of exchange. Milestones at the molecular level were the discoveries of the structure ofDNA, RNA, andproteins. It is not by coincidence that this exchange has intensi?ed in recent years. Laboratory experiments reach down to the level of single molecules. Moreover, thereisnowavastamountofgenomicinformation, whichisstillgrowingex- nentially due to the various sequencing projects. Biologists increasingly feel the need for theoretical models...