It's hard to believe that bikini-loving Serena Williams was once insecure about her body. "I grew up with a lot of sisters -- I was the youngest, and I was really thick. ... Being in a society where a lot of people are really thin, it was hard ... especially as an athlete," the tennis pro has said. "I had to learn how to embrace myself and embrace my curves." Embrace she has! So in honor of Serena's 32nd birthday on Sept. 26, let's click through to see the superstar athlete in all her beach-bound glory.