Check out how these 15 celebrities have aged over the years

Science has yet to figure out how to stop the ageing process and one day or another, we'll all find our first gray hair or wrinkles.  Women tend to get a hard deal, particularly if they've gone through the grueling pregnancy process and even super-rich celebrities can only rely on fillers and cosmetic surgery for a limited amount of time.

Here are 15 photos of celebrities that show how they've aged. What do you think?  Still looking hot or on a downward spiral?

1. Jennifer Lopez

2. Pink

3. Beyoncé

4. Kelly Clarkson

5. Russell Crowe

6. Rihanna

7. Christina Aguilera

8. Tyra Banks

9. Steven Seagal

10. Aishwarya Rai

11. Alyssa Milano

12. Kate Winslet

13. Avril Lavigne

14. Mariah Carey

15. Kim Kardashian