Paola Kudack/ELLE

In just 10 years, Mary-Kate and Ashley Olsen have become one of the most lauded design teams in fashion, a fact that surprises no one more than them.

"It's hard to believe it's been 10 years," Mary-Kate said of their label, The Row, a nod to Savile Row tailoring, in an interview with December's Elle magazine. Every move that we've made through the past 10 years has been step-by-step," Ashley said.

"One item at a time," Mary-Kate added. "We sit and look at everything in every possible version of how you might wear it. We are all about making our clothes work with reality."

But when the 28-year-old child stars left Hollywood for New York City 10 years ago to reinvent themselves as designers, cynics questioned whether they were just playing an expensive game of dress-up.

"People were asking us all sorts of questions in the beginning," Mary-Kate said.

"It went beyond skeptical," Ashley added. "You just have to put on blinders and do your work."

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That's exactly what they did. Launching in 2004 with a perfect white T-shirt, they focused on fit and fabric, methodically setting out to create the perfectly cut tank top next, then $1,000 leather leggings, followed by the perfectly tailored blazer.

"I think we do things because we stare at them for too long," Ashley said with a laugh.

Their method works. The label generates tens of millions in sales and is carried in more than 145 high-end boutiques and department stores in the United States, like Barneys, Bergdorf's, Neiman Marcus and Saks, as well as in London and Paris. Their accessories are sold in more than 77 stores, with prices ranging from $1,000 to $39,000 for an alligator-skin backpack.

The fashion industry has also embraced the Olsen twins, awarding them CFDA Womenswear Designer of the Year in 2012 and CFDA's Accessories Designer of the Year this year.

Last May, they opened their first Los Angeles store, on Melrose Place.

"Our client is very understated, but she's happy to spend the money," Ashley said.