Kay Panabaker was 10 in Monsters, Inc. when she played the character 'Additional Voices (voice) (uncredited)'.
That was over 22 years ago in 2001.
This was her first recorded movie acting credit (although may not technically be her first actual acting role).
Today she is 34, and has starred in 15 movies in total, 14 of those since Monsters, Inc. was released.
In Monsters, Inc., I think Kay Panabaker looks: