There's one thing that always binds together Ellen von Unwerth's inimitable photographs: a distinct sense of playfulness. Although she's best known for provocative, sexy images that fully capture the beauty of her famous subjects -- Madonna, Lady Gaga, Naomi Campbell, Beyoncé among others -- she also worked as model. "I was a model for 10 years and I was so frustrated, I was lively and always had fun ideas but the photographers were always like, just stand there, look to the left, look to the right, don't smile," she said in a phone interview. "So when I started to shoot my model girlfriends I did the opposite. I wanted to catch something, a slice of life I always called it. I actually try to make it look like a stolen moment."