In the '90s and early '20s, crimped hair made an appearance at every red carpet event (and unforgettably, on Christina Aguilera in the 2001 "Lady Marmalade" music video). And because the trends of ...

Back in the early 2000s, all the cool girls crimped their hair. Hilary Duff, Britney Spears, and Beyoncé all did it — and if you were a Millennial with a hot pink flat iron, you probably did it too.