The 11th, 11 years later.
In many ways, it became the reference point for a lot of questions, fears, and discussion we share about security. There have been numerous defining moments in history: depending on your age and cultural context, you may vividly remember where you were when JFK was assassinated, or your reaction when the Challenger spacecraft exploded.
I was sitting in my biology class when the first tower was hit on 9/11. My teacher had hurriedly dragged in an old TV and we all sat in stunned silence, our eyes glued to the scenes before us.
It was a surreal experience - and I couldn't even begin to imagine the impact it would make on the entire world for years to come.
There's been a lot of fiction that's come out since the attacks in 2001. Here are a few to check out about relationships entangled in the events of that day.