"The lads from Liverpool" led a musical cultural exchange that impacted everything from fashion to sexual mores to politics. Graham Nash, Smokey Robinson and more recall what it was like to make music that mirrored the souls of the young.

Astronaut and NASA Administrator Charles Bolden, astronauts Mike Massimino & Dave Scott, Tom Hanks and others describe the greatest adventure story of all time. The "giant leap" pushed the boundaries of exploration to an unprecedented frontier.

Tom Hayden, Gloria Steinem and others discuss one of the most dramatic years in U.S. history. A Soviet incursion, assassinations, the wars in Southeast Asia, violence at the Democratic National Convention and the election of President Nixon.