Dakota & Elizabeth 'Very Good Girls' ... In Bikinis

7/16/2012 12:55 PM PDT

Dakota Fanning & Elizabeth Olsen -- 'Very Good Girls' in Bikinis

Former child star Dakota Fanning,18, and Mary-Kate & Ashley's little sister Elizabeth Olsen, 23, went two pieces on the set of their new movie "Very Good Girls" in New York over the weekend.

In the flick, the bikini-clad actresses play friends who make a pact to lose their virginity during the summer after graduating high school.

They grow up so fast.