Mathieu Kassovitz was 10 in Make Room for Tomorrow when he played the character 'Mathias Oppenheim'.
That was over 45 years ago in 1979.
This was his first recorded movie acting credit (although may not technically be his first actual acting role).
Today he is 56, and has starred in 56 movies in total, 51 of those since Make Room for Tomorrow was released.
In Make Room for Tomorrow, I think Mathieu Kassovitz looks: