Kate Winslet: Good Genes or Good Docs?!

Kate Winslet's looks will never let go!

Here's a 21-year-old version of the "Titanic" actress at an awards show in Los Angeles back in 1996 (left) and 18 years later... the A-list actress and mother of three -- who celebrates her 39th birthday this weekend -- at a film festival in Toronto last month (right).

Unsinkable.