When we think of Gwen Stefani, we immediately think — impossibly cool. The artist, designer, and seriously hot mama founded a career, first as singer and songwriter for No Doubt, then secured her status as an accomplished American designer with her line L.A.M.B., and later with the launch of her Harajuku Lovers in 2005. Likewise, her personal style has evolved from a sporty punk aesthetic in her early days to a more polished rocker vibe that makes her one of our favorites to watch. Signatures stay the same — coiffed blond locks, bold red lips, rock hard abs, and an affinity for labels like Galliano and Vivienne Westwood — and of course, designs from her own coveted label. Still, Gwen continues to transform, showing a softer side via flowy maxi dresses, other times, flaunting her figure, and reminding us that she's still got some of the hottest abs we've ever seen. And, since today is Gwen's birthday, we thought it only fitting to pay tribute to her stylish evolution. Click through for 40 of her most memorable looks that highlight her growth from rocker upstart to glam icon, and join us in wishing the very talented, and ridiculously cool, Gwen Stefani a very fab birthday.