Leighton Meester was 16 in The Big Wide World of Carl Laemke when she played the character 'Tanni'.
That was over 21 years ago in 2003.
This was her first recorded movie acting credit (although may not technically be her first actual acting role).
Today she is 37, and has starred in 28 movies in total, 25 of those since The Big Wide World of Carl Laemke was released.
In The Big Wide World of Carl Laemke, I think Leighton Meester looks: