Celebrity Hair Trend: Sleek Low Ponytails on Rihanna, Gwyneth Paltrow, Alessandra Ambrosio, Camilla Belle

Nearly showing nipple wasn't the only big trend among the celebrities at last night's amfAR Inspiration Gala in Hollywood. Everyone's all about hair worn low, parted, and slicked back (into a ponytail, bun, or braid—anything goes in back). Just witness all the different glamorous variations seen on the red carpet.

Alessandra Ambrosio did a stark center part—most flattering on people with symmetrical features like hers.

Rihanna took her part way low and to one side, offset by a dramatic front swoop.

Gwyneth Paltrow was team center part, framing statement red lipstick.