We know what Mary-Kate and Ashley Olsen did this summer!

The acting and designing duo have been hard at work on TheRow.com, the first e-commerce site for their megapopular three-year-old fashion label that launches today!

"We focused on The Row's e-commerce experience to be engaging, effortless, and as user-friendly as possible," Ashley said in a statement. "It's a natural extension and next step to building The Row's lifestyle brand."

To replicate the in-store experience, the dark and moody site features 360-degree views of each piece of clothing, which hang in a virtual shop among mid-century furniture.

The Olsens also demonstrate their film savvy in the site's Media section, where visitors can check out video from their Fall 2010 runway presentation and a somewhat haunting backstage film by hip photographer and filmmaker KT Auleta showing models preparing for the show while a spare piano instrumental of The Pixies' "Where Is My Mind?" plays in the background.

Vintage cinema noir vignettes -- an ashtray with lit cigarettes sits atop a dress; a blouse billows in the wind -- also introduce each category of clothing, while a News section keeps shoppers up to date on sample sales and other events.

The first items up for sale will be from the Fall 2010 women's collection, with offerings from the men's line following later this year.

To usher in the arrival of the new site, The Row is offering a few perks. First, if shoppers enter the checkout promo code SHOPTHEROW between now and Aug. 20, they'll get 15 percent off their entire purchase.

And if fans sign up for the site's mailing list before Aug. 20, they'll also be entered to win a pair of The Row's smoking-hot leather motorcycle pants.

Keep clicking to see which other celebrity sisters -- hint: there are three of them -- are launching their own fashion, home, and accessory lines.