How could a tiny Tyrannosaurus rex baby grow into a six-ton super carnivore? Dinosaur builder Hall Train and renowned paleoartist Jason Brougham team up with top scientists to uncover the truth about this fascinating creature and to create the world's most accurate, fully skinned, mechanical replica of a walking juvenile T. rex. Join National Geographic as the hidden secrets of the Tyrannosaurus rex are revealed. (52 minutes)