KATE BECKINSALE, 39
What's black and white and fit all over? Beckinsale, who sports the classic color combo for an afternoon of sunbathing in Mexico. It's no wonder she was named Esquire's Sexiest Woman Alive a few years ago. To get the British beauty's incredibly toned booty, her trainer Mandy Ingber, tells PEOPLE they work on yoga poses with an emphasis on squats, lunges and plié squats.