Zac Posen: Fashion's 'It' Boy at 23

Zac Posen (search) starts his day like many other 23-year-olds: He's running late and clutching a Starbucks iced coffee. His pants are slightly rumpled and the polo shirt-funky blazer combination he's wearing is an unconventional interpretation of business casual.

But the difference between Posen and the throngs of other young up-and-comers in the fashion world is he doesn't have to answer to anybody when he makes it in to work -- he's the boss.

It's because of his early success as a designer, including a Council of Fashion Designers of America (search) award for emerging talent and a joint venture with Sean "P. Diddy" Combs that will soon splash Zac Posen's name onto handbags and other accessories, that his studio in downtown Manhattan is all abuzz on this particular morning in preparation for New York Fashion Week (search).

The spring 2005 collection will be a further expansion of Posen's line, which has grown from celebrity eveningwear to suits and now sportswear. It's sportswear for a certain kind of customer, though, since not everyone wears an embellished knit polo dress to their grocery store.

"The Zac Posen woman is an intelligent woman who loves rare and exceptional things. She's adventurous and extremely sexy. ... Personal style is part of her way of thinking, of shopping and buying," Posen said.

His muse is his sister and creative partner, Alexandra. "I'm trying to create clothing to fit her fantasy," Posen said.

Other women in Posen's posse include longtime friend Claire Danes, Natalie Portman, former "Hairspray" star Marissa Jarent Winokur and Demi Moore, who posed, wearing a siren's red satin gown, with the designer in Vogue last year.

And there's his mother, Susan, too. She represents the business side of the Posen trifecta at the family-run company.

Right now, Posen says he doesn't have a lot of time to enjoy the fruits of his labor -- save the occasional dinner party he throws for friends or meal at a restaurant near his new apartment.

"I am planning to grow a global empire, so that takes a lot of time."