I've seen the footage countless times, but with each viewing something new strikes me - something I might not have noticed before.
Today I saw a young girl with blonde hair who was crying as the fireman doused her head with bottled water - to wash off all the toxic ash and soot.
She was probably just nine or 10. The same age as my daughter Ellie was that day. Maybe she started college this fall, too, and had her prom last spring.
So much time has passed, and she's a young woman now. I wonder what she remembers - if her friends ever talk about what they experienced that morning.
Peggy Noonan wrote about an unexpected stage of grief, "the fear that the ache will go away."
Sometimes you think it has, and then you see an image of a little girl covered in dust and you know it never really will.
That's a page from my notebook.
I'm Katie Couric, CBS News.