Jennifer Aniston turns 43 today! She found fame back in the '90s on Friends, but since her days of playing Rachel Green, she has become one of the biggest actresses in the world. Jen has a lot to smile about between her sexy big screen costars, famous friends, and red-hot romance with Justin Theroux. In honor of her birthday, we've rounded up some of her happiest moments over the years. Click through to see them, and happy birthday to Jen!