Season 2, Episode 4 Nova scienceNow

First Aired: July 24, 2007

How environment may influence DNA; the "Kryptos" sculpture at CIA headquarters, which contains coded messages; homemaker-turned-paleontologist Mary Schweitzer, who discovered spongy tissue in a 68 million-year-old T. rex; Duke mathematics and physics professor Arlie Petters, who is working to prove the "braneworld" theory of gravity, which posits that there are five dimensions (four spatial, plus time).