The 9/11 Memorial & Museum faced a daunting challenge: how do you tell the story of the September 11 terrorist attacks at the World Trade Center without making it unbearable? How do you memorialize a day most of us wish we could forget? In 2013, Lesley Stahl visited the museum at Ground Zero, a year before it opened and explored its most challenging debates. Today marks 24 years since the September 11 terrorist attacks. | 60 Minutes