Mel Rudder, who grew up in the affluent '90s with parents who "provided well" for him and his siblings, graduated from his Louisville, Ky., high school in 2001 with complacent optimism about his future.
But during his first week of college at Virginia Tech in Blacksburg, everything changed.
Long before smartphones and iPads, students began screaming in the hallways that the nation was under attack, Rudder said, and he rushed into the dorm lounge to witness the North Tower of the World Trade Center collapse at 10:28 a.m.
His grandmother and aunt, both from Barbados, had worked in the neighborhood. "Miraculously, no one was there that day," he said.
"Being a freshman, I felt like my world had turned upside down," Rudder said. "Nothing traumatic had ever happened in my life. It was all flowers and rainbows. It was a shocker and it made me realize how the real world is."
For Rudder, 28, and his classmates, 9/11 and the political world view that followed came to define their coming of age. Some, like Rudder, joined the military and went to war, but others, like classmate Valerie Szybala, chose to learn Arabic and work for peace.
Szybala took an interest in global affairs while a student at West Potomac High School in Alexandria, Va., after traveling with a youth group to Israel in 2000 before the second intifada.
She went on to graduate school at Stanford University to get a degree in international political studies and later lived in the volatile West Bank. At first, her parents questioned her career choice.
"Both of my grandparents served in World War II," Szybala, 28, said. "My parents aren't the most political people ever and they were more in my face about the fact that they worked their way up from nothing. That I had it so easy."
Her paternal grandfather was a line worker at a General Motors plant in Buffalo, N.Y., and her mother's family had grown up in the projects of New York City.
As an adolescent, Szybala said, "If I had something to rally around I didn't know what it was, or I was too young and not thinking about those kinds of things."
As the 10th anniversary of 9/11 approaches, Osama bin Laden, who ordered the attacks on U.S. civilian targets, has been killed by Navy Seals and a so-called Arab Spring has brought political uprisings across the Middle East.
The tumultuous decade has been marked by two wars, natural disasters in Thailand, New Orleans and Haiti, the election of the nation's first black president and an economic meltdown.
During that time, Rudder and Szybala graduated from college, found careers and forged into adulthood. Though they were not there, their alma mater, Virginia Tech, saw the second worst mass murder at a college when 32 people were killed and 25 others wounded on the campus in 2007.
But on that sparkling blue-sky day in September 2001, the world changed in an instant when they were still teenagers.
Judy Kuriansky, a psychologist who volunteered with the Red Cross, counseling students near ground zero in the aftermath of the attacks, said many teens experienced depression -- "not feeling they had a future."
"They were adolescents at the time," said Kuriansky, who later worked in the 2010 earthquake in Haiti. "They were just stepping into their careers and love lives."
In a study of those affected by the national tragedy, Kuriansky said, many asked themselves, "What is my future going to look like and is there a future? Several of them sensed it was the end of the world?"