A look back at 9/11, 25 years later.

On Sept. 11, 2001, four planes were hijacked. Two flew into the World Trade Center, one into the Pentagon, and the fourth crashed into a field in Pennsylvania. Then, everything changed. Those who are old enough will never forget where they were that day, but to a growing number of people, it is history. We look back on our immediate reaction and the lasting impact of those terrorist attacks.