What I remember about Semptember 11th

I heard A LOT about September 11th on the news, people chatting, at school and whole family. It was devastating to me what these terrorists did. Why did they do it? Maybe some scientists know why they did it, but I want to know for myself. A lot of people were crying, people lost plenty of family and friends. People worked at the twin towers. I wouldn't know where to run to the nearest exit. People that worked at the very top of the building would die instantly because that is where the plan hit.