The Olsen Twins: We Work Until 4 a.m.

 Kevin Mazur/

Sounds like Ashley and Mary Kate Olsen are not afraid to burn the midnight oil.

At only 24, the hard-working twins are Hollywood veterans. But, thanks to their highly successful fashion lines, these days they're more known as respected designers.

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"We are in such a unique situation," Ashley Olsen told WWD. "People have been watching us since we were nine months old."

The Olsens first launched The Row in 2007 and followed with the contemporary line Elizabeth and James (plus a tween line, Olsenboye, sold at J.C. Penney). Stars like Heidi Klum, Jessica Biel and Olivia Palermo have been spotted in the fashion labels.

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For the sisters who have been working since they were babies on Full House, they remain very hands on.

"We are in the office by 9 a.m., depending on where we are in the season," Ashley explained. "It's not unusual for us to be in the office until 4 a.m."

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And with big plans on the horizon (The Olsens say they're planning to launch handbags to The Row for next fall), it doesn't sound like the sisters will be going to bed early any time soon.

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