PLEASE NOTE: EDIT CONTAINS CONVERTED 4:3 MATERIAL.

These days for some simply being a celebrity just isn't enough.

Over the past few years an increasing number of celebs have tried their hand at design - trying to turn their passion for fashion into a business.

Tracy Taylor, the U.S. editor of NET-A-PORTER.COM explains it's not as easy as it looks.

SOUNDBITE: Tracy Taylor, U.S. editor of NET-A-PORTER.COM, saying, (English):

"I almost think it's more difficult for a celebrity to launch a clothing line. Honestly, the eyes and ears of the world are on them. Not only are the eyes of the customer on them, but the eyes of this rarified group that almost is unattainable for celebrities and that's to be a fashion designer."

One starlet who has found success in the world of design is celebrity stylist Rachel Zoe.

Zoe has transferred her status as a front row regular into a major player in the fashion industry.

But she says her launch was nothing short of daunting.

SOUNDBITE: Rachel Zoe, designer, saying (English):

"To then have my collection out on display for everyone to see, my peers, mentors, and then, of course, buyers, customers, editors, photographers - the whole thing is terrifying."

Women's Wear Daily fashion features editor Marc Karimzadeh points to singer Jessica Simpson as a star who is practically in a class of her own.

SOUNDBITE: Marc Karimzadeh, Women's Wear Daily fashion features editor, saying, (English):

"Jessica Simpson is one of those rare examples of a celebrity that has built a business based on a master license and all different kinds of sub-licenses. In the process, she has created a billion-dollar business, which is really remarkable. I can't think of any designer that has been in business for as little as she has, having had that same type of success."

Another celebrity-turned-designer who has had great success is Victoria Beckham, formerly known as "Posh Spice" from the Spice Girls.

SOUNDBITE: Tracy Taylor, U.S. editor of NET-A-PORTER.COM, saying, (English):

"She wasn't just a Spice Girl to us. We could tell very early on that she had an incredible design aesthetic and sensibility. I think what really put Victoria Beckham on the map was this incredible silhouette of a dress."

Actresses Mary-Kate and Ashley Olsen are another success story with three successful brands.

Speaking at the Thompson Lower East Side Hotel in New York, Taylor says their attention to detail sets them apart.

SOUNDBITE: Tracy Taylor, U.S. editor of NET-A-PORTER.COM, saying, (English):

"Their detailing is exquisite. You'll have something like fully workable button holes, which only really you would find in men's suiting. You have these amazing rope shoulders - the cut is incredible."

So is there a key to making a successful transition from walking the red carpet to being worn on the red carpet?

Taylor says yes.

SOUNDBITE: Tracy Taylor, U.S. editor of NET-A-PORTER.COM, saying, (English):

"There is definitely a secret to making a celebrity line successful, and that is really knowing exactly who is it you're focusing on, and doing whatever it takes to get to them."

Rachel Zoe will present her Fall 2012 collection at Mercedes Benz Fashion Week in New York.

Alicia Powell, Reuters.