"I started collecting when I was 9 or 10," says Mathieu Bitton, Lenny Kravitz's photographer who also happens to be (arguably) the world's most avid Prince memorabilia collector. "I had to have every print and every pressing from every country." Bitton's scrounging and decades-long persistence paid off, however, when the budding art director was tapped to design Prince's Ultimate Prince CD box set (photos ahead). Since then, Bitton has collected countless of rare and one-of-a-kind Prince-related items, from a pair of blue heels (he won't tell us how he got them, just that "they're from someone special") to a rare "The Next Birthday" record (to celebrate Prince's own birthday), complete with yellow panties and matching vinyl. Bitton shared with Billboard, exclusively and in his own words, his massive and all-encompassing collection.