Buns, Undone: Cameron Diaz's messy 'do mirrors the hair styles at Charlotte Ronson's and Lanvin's Spring 2010 fashion show. Photo: Getty Images

Ballerina buns are one of Spring's biggest hair trends.

Now, these aren't the super slicked, ear-pulling buns you paired with white tights and pliés in your childhood ballet class. The buns we saw on the spring runways were very "I don't care," worn, we imagine, by a slacker ballerina who's late to practice because her motorcycle broke down.

They're perfectly imperfect, full of "wispy imperfections" as lead hairstylist Anthony Barrow told us backstage at Charlotte Ronson.

Already glimpsed on New York City's downtown set, (we were admiring a model type's wickedly wound creation in a NoLIta bar over the weekend), Cameron Diaz is the first celebrity to wear the trend on the red carpet.

She wore the hair style last night to the premiere of 'The Box' in New York City, with face-framing wisps of hair and a golden statement necklace. Which works, because the great thing about subversive ballerina buns is that there are no rules. It was seen on runways as different as Charlotte Ronson, Lanvin and Ruffian, and paired with fashions that ran the gamut from frilly frocks to glamorous suits.

So invest in some bobby pins and practice your rusty bun winding techniques. You're a ballerina, and you're bad to the bone.