That's especially true for children who weren't even born yet. CBS2's Alice Gainer spoke with students about their experience at the site in Lower Manhattan.
"I was born November 11, 2001. So just right after," said Presley Pyle, 19, of Oregon.
For those not yet born on 9/11, the classroom -- in some cases, thousands of miles away -- has been the only place they're learned about it.
"They only showed videos and gave us a little homework about it," said Anika Shukla, 14, of Connecticut.
"My parents didn't really talk about it, and I didn't really ask," said Cameron Kretzschmar, 19, of Oregon.
"We learned about it a few times, like on the anniversary and stuff," said Will Stasik, 13, of Michigan.
Complete Coverage: 9/11 Twenty Years Later
But after making their way through the memorial and museum, these kids and teens took Gainer through their experience.
"How different it is than in school. They have all the firetrucks and stuff that got crushed during it," said Aaron Degray, 13, of Rochester. "I was sad and just like, why did they do it?"
"I kind of felt like crying, because it was really sad and it was really quiet inside," said Avani Shukla, 10, of Connecticut.
"She got herself a golden ring in remembrance of surviving that first attack, and it was found in the remains," Kretzschmar said. "I think that's what hit me hardest the most."
"I was like, 'Wow, what happened?' I was really sad," said Avika Gupta, 12, from Seattle.
"How scared they would have been when they heard that they attacked," Shukla said. "As well as people outside watching it happen."
"You realize what people went through to try to save people in the towers and how many people lost their lives doing their job in the line of duty," said Pyle. "That was definitely one of the most impactful parts for me."
The students told Gainer marking 20 years since the attacks takes on greater significance to them now.
"I wasn't really expecting it to hit me as hard as it did when I went in there," Kretzschmar said.
"You're not outside looking in anymore. You've been to that location and you almost feel, even though I wasn't even alive at the time, it's much more of a connection to it and much more of a solemn respect for all the people that were here," Pyle said.
These students, despite not being alive at the time, vow to never forget after seeing the exhibits, footage and artifacts.
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