Today is AJ Michalka's 24th birthday, and we can't believe it! We've been following the actress and Aly & AJ and 78violet singer for years now, and she has totally transformed right before our very eyes.
From more laid-back styles to glam red carpet looks, AJ has changed so much! We just had to round up her most memorable outfits in honor of her special day.
Click through the gallery to see AJ's complete evolution. Then, don't forget to wish her a happy birthday in the comments below!