It's hard to forget where you were on September 11, 2001, the feeling of horror and utter disbelief at what was happening – the largest terrorist attack our generation and perhaps the world – had ever witnessed.
The ensuing 24-hour coverage was hard to ever forget.
However, for those there on the day, the mental and emotional scars are difficult to heal.
The first of the four co-ordinated terrorist attacks – orchestrated by Osama bin Laden, founder of the extreme militant Islamic terrorist organisation al-Qaeda – hit the North Tower of the World Trade Centre complex in Lower Manhattan at 8.46am, just as ordinary workers were starting their day on Tuesday, September 11, 2001.
In total, 2996 people lost their lives after that day in horrific scenes – orchestrated by the now deceased Osama bin Laden, founder of the extreme militant Islamic terrorist organisation al-Qaeda – that have never been witnessed before or since.
Countless others were injured, families were torn apart and many still suffer two decades later from the trauma of that day.
Miraculously, some lived to tell the tale.
New Yorker Pasquale Buzzelli, whose wife Louise at the time was seven months pregnant with their first child, a daughter named Hope – was one of those people.
A structural engineer with the Port Authority, Pasquale had just arrived at work, and was making his way to his office on the 64th floor of the North Tower of the World Trade Centre.
"The elevator started to, to move, and we started to go up, and then, all of a sudden, the lights flickered, the elevator shook, uh it felt like it dropped, maybe, you know, a foot or so, and uh, we just looked at each other, like, 'What, you know, what just happened?'" he told 60 Minutes.
Unknown to Pasquale at the time, 29 floors above, American Airlines Flight 11 had ripped through one of the world's most iconic buildings.
So I called her and I said, "Louise," I said, "Don't be alarmed, I'm okay, everything's fine, just, can you put the television on, and tell me what you see, and she goes, 'Oh my god,' she goes, 'A plane hit your building.'"
Pasquale was one of only two people who fell with the towers and survived and one of only 16 who would be rescued from the rubble.
He fell 18 floors as the North Tower collapsed, sat on a tiny concrete slab, and miraculously, survived.
He had a broken foot and a few burns and scrapes but remarkably was otherwise unharmed.
"I still remember the smell, I still remember the sounds," Pasquale told Channel 9's 60 Minutes' Tara Brown.
"I could – pretty much run through it in my head, you know, step by step, you know, uh, like a video."
Before his fall, his wife, Louise, said, Pasquale called home for a second time.
"I said 'Where are you,' and he said, "I'm, I'm still here, I'm here,' and I said, 'You're still in the building?'
"I said, 'Get out, why are you still there, and I'm so angry,' you know, and he was like, 'No, no, the floor is fine. It's OK up here.'
But urged on by the smell of smoke from the fire burning above, Pasquale realised it was time to go.
"And we said, you know, what the F? 'What are we still doing here' OK lets get out of here.
"We gathered everything, uh flashlight, we wet down some towels and stuff, and we started our way down the stairs."
At 9.59am, the South Tower suddenly collapsed.
By now in the stairwell of the north tower Pasquale and his co-workers felt the building shake but at that point, they were still completely unaware the South Tower had collapsed or of the terrible danger they were in
"So we, we continued our way down, we passed, firemen they just said, you know, "Keep going, it's a straight run, keep going, keep going, "Pasquale said.
"And then, we went down maybe couple more flights, and it was, on the 22nd floor that all of a sudden, you know, everything started to shake.
I heard screaming, you know, people behind me screaming, and then, just everything went dark."
"The building started to shake violently. I heard all the, the loud rumbling from above, I dove into a corner, and I got into a foetal position, and just buried myself up against a corner, so if anything large or heavy was falling, at least I had two sides that could protect me.
"I felt the wall that I was laying next to, just crack and the floor give away, and I stayed tucked in the foetal position with my eyes closed.
"I felt this, this wind rush, as I was falling and, you know, this abrasive, sandblaster type feeling, and I just stayed tucked in, I was being knocked around. I saw, you know, a few flashes of light from being knocked in the head. I just remember saying, you know, 'I can't believe this is how, my god, I can't believe this is how I'm gonna die.'
"Uh, you know, I thought about my wife, my unborn child ... and, you know, I said, 'Please just God please take care of them and make it a quick death.'"
Reflecting back, Pasquale said, "I still remember that feeling, you know, free falling. When I woke up and I opened up my eyes. I was like, 'This is impossible, I don't know how I could have possibly survived that?'"
His wife, Louise, said, "You feel like, so much life has happened in this time, right? But then it feels like it was just yesterday."
Pascale added, "To be there in the days immediately after the attacks was a surreal experience.
"There were so many accounts of split-second decisions that meant the difference between life and death.
"Everybody said, 'Oh, you, you know, you're alive for a reason, you must survive for a reason, you're here to do some amazing things.'
"… I just wanted to have a normal life – and, and be there for our family.
"I mean, I guess I wanted to make sure I didn't screw up, you know," he added, laughing.
"Here I am given this gift, and I wanted to make the most of it."