Many women, even today, are still influenced by Marilyn Monroe- and Katy Perry's no exception. Aside from its color, this medium bob hairstyle is a lot like the kind of hairstyle Marilyn was wearing in the 40s and 50s. It's an upswept 'do dressed in large waves to create movement and body through the edges. All of these retro hairstyles for women are reinventing vintage hairstyles of the 1920s-50s ever so slightly, creating cool "retro vintage hairstyles." If you're interested in trying one yourself I'd recommend talking to your stylist about which one could suit your face shape and hair type and texture- and of course your lifestyle (because some of these hairstyles are quite high-maintenance).