By Caitlin Petreycik
Oct 25, 2011 @ 10:50 am
Ramey Photo; Seth Poppel/Yearbook Library

Happy Birthday, Katy Perry! Mrs. Russell Brand turns 27 today, and in celebration, we're taking a look back at the California girl's transformation from blond high school student to rainbow-haired pop star. See Perry's beauty evolution in the gallery!

MORE KATY PERRY:Katy's Costume SecretsTry On Katy's Lavender HairKaty's October InStyle Cover