Duff may have come a long way from her Lizzie McGuire days, but her lively spirit (as evidenced by her Instagram) keeps her young at heart—even she gets pumped up for a Justin Bieber concert! We can only imagine how much fun she and her 3-year-old son, Luca (with ex, Mike Comrie), must have together.
Currently, the talented performer is keeping busy promoting her latest studio album, Breath In. Breathe Out., as well as her upcoming second season of TV Land's Younger. We predict a long career in the making.
Celebrate Duff's special day with a look at some of her most entertaining selfies, starting with the one above: