Willow Smith was 6 in I Am Legend when she played the character 'Marley Neville'.
That was over 16 years ago in 2007.
This was her first recorded movie acting credit (although may not technically be her first actual acting role).
Today she is 23, and has starred in 13 movies in total, 11 of those since I Am Legend was released.
In I Am Legend, I think Willow Smith looks: