Modern Marvels: This episode goes behind the scenes of the world's largest communication agency to show how the mail gets through. Follow a typical letter on a remarkable journey where human hands may only touch it twice. Learn how the Post Office has changed through the years and get an up-close look at the technology the modern Post Office relies on. Historians probe the long past of the agency and reveal its gaffes and triumphs, while archival footage recalls the glory days of twice-daily delivery. And Postmaster General Marvin Runyon offers a privileged view of today's Post Office and the problems it faces as it prepares for a new millennium.