Mathieu Amalric was 18 in Favourites of the Moon when he played the character 'Julien'.
That was over 39 years ago in 1985.
This was his first recorded movie acting credit (although may not technically be his first actual acting role).
Today he is 58, and has starred in 125 movies in total, 124 of those since Favourites of the Moon was released.
In Favourites of the Moon, I think Mathieu Amalric looks: