Reese Witherspoon turns 37 today. She got her start in Hollywood almost 20 years ago and has been a bright spot on the scene ever since. Reese has a lot to smile about these days — she's approaching her two-year marriage anniversary to husband Jim Toth; gave birth to her third child, Tennessee James, in September; and has Mud hitting theaters in April. From award shows and red carpets to working out, Reese's infectious smile and ear-to-ear grin are sure to make you crack a smirk too. Click through to see some of her sweetest smiling moments through the years!