Stella McCartney has spent many of her summer days in the Hamptons and this August afternoon is no different, except that I have the good fortune of being there with her. 20/20 has scored an exclusive invite to her high-fashion-meets kids’ party at the Fireplace Project in East Hampton—a small auto-garage-turned art gallery, and for just this one weekend, turned pop-up shop for McCartney. An array of coats, skirts, boots and purses are displayed beneath a tent for guests to peruse while sipping cocktails, while the vintage-inspired eyewear sits perched atop the plastic faces of blow-up dinosaurs and donkey piñatas, embracing the childish alter ego of the affair. Out in the parking lot there are pony rides and an activity table set up at which children can pet bunnies, make Play-Doh concoctions and nibble on candy necklaces.

The event is meant to be low-key but you’d never know it from the guest list, which is a celebrity feast for the eyes. Everyone looks like they’ve just rolled off the beach, casual and sun-kissed, and they probably have. Stella’s father, former Beatle Paul McCartney is bedecked in a T-shirt and surf shorts, and chats casually with Gwyneth Paltrow. Paltrow is keeping an eye on her daughter, Apple, who is thoroughly enjoying a pony ride alongside a very cute blonde boy, who happens to be the son of Naomi Watts and Liev Schreiber, who are also standing watchfully nearby. When Stella arrives, she brings her own young children who run around, hyped up on the festive day (and given the spread on the activity table, probably a bit of sugar) with Paltrow’s kids and, to my endless celebrity fascination, with Paul’s young daughter from his marriage to Heather Mills; they are not so different in age. Later, back in the grown-up side of the event, I happen upon Stella selecting several pieces of her ready-to-wear off the racks and telling her good friend, “Gwyny, you’ve got to try these.” This is McCartney’s world.

Stella McCartney’s celebrity has been hard-earned and she has finally been recognized as a talented McCartney in her own right. Since she appeared on the fashion world radar many were eager to declare she was riding the acclaim of her parents, Paul and the late Linda McCartney (a noted photographer and member of Paul’s post-Beatles band, Wings) and prophesied a short-lived design career. (We have all borne witness to the celebrity child phenomenon of questionable music careers and self-promoting perfume lines, after all.) Yet, the longevity of the Stella McCartney brand has dispelled doubts about her ability and has propelled her to the ranks of high fashion and self-won fame.

Fashion has been McCartney’s intention all along and she has been known to remark when interviewed that she would have been a fashion designer regardless of whether Paul McCartney had been, well, the Paul McCartney. When she was 12 she was creating her own designs and by 15 she apprenticed for renowned fashion designer Christian Lacroix. McCartney went on to create her own line in 1995 before being appointed chief designer for Chloe two years later. She was recruited by the Gucci Group to establish her brand and ever since, has secured herself a recurrent spot in Fashion Week runway shows and has spread her empire worldwide with store locations in New York, Los Angeles, Paris and Hong Kong. Her following is such that she has been enthusiastically snatched up for collaborations with big-name labels such as Adidas, Puma, LeSportsac and Gap. Not to mention the one-time line she designed for H&M that created a Tasmanian-devil whirlwind in stores and left the racks picked clean in a matter of minutes.

When I speak to McCartney, we discuss her latest partnership—her license with Luxottica. She comes off as down-to-earth and humble while describing this new incarnation for her eyewear, which she has been designing since 2003. She has signed on for an initial term of six years with the first crop of Luxottica-licensed sunwear debuting this fall. “The great thing about Luxottica is that we have similar interests,” she says. “They didn’t have to work with a small niche designer like myself, but this was what they were looking for. We are a small brand and having the opportunity to work with a company like them is amazing.”

And the enthusiasm about the licensing agreement comes from both sides of the coin. Pierre Fay, executive vice president of Luxottica Wholesale notes, “We are very excited to introduce Stella McCartney eyewear. Her style is sophisticated and innovative and her environmentally friend ly concepts are a perfect fit for our brand portfolio. We look forward to the fresh, bold styling that she will bring to her eyewear collection.”

Staying environmentally friendly is a cornerstone of Stella’s world. Yes, she is a fashion sensation, her best friends are Madonna and Gwyneth Paltrow, and she has one of the world’s most famous parental units, but she sticks to her laurels and has never lost sight of one of her dearest causes: animal rights. A steadfast activist for PETA (People for the Ethical Treatment of Animals), she has merged her two passions, never using leather or fur in her designs and using organic materials whenever possible. The Stella McCartney enterprise covers a vast range of products—lingerie, perfume, handbags, you name it—and they all adhere to her animal-friendly mantra. Amidst the vegan hors d’oeuvres and small-scale petting zoo, McCartney comments about the importance of designing green. “I’m very conscious about using recycled materials and natural things like wood,” she says. “The great thing about sunglasses is that you very rarely come into contact with fur or leather. It’s a great product to work on when you’re ethically minded.”

There is a lot of calculation that goes into McCartney’s designs, balancing earth-friendly materials with the right aesthetic. Her beliefs maintain a steady backbone for her fashions, while her design inspirations are ever-changing. “I look at old films, old magazines or art exhibitions,” she says. “Sometimes I’m inspired by architecture; sometimes strange, obscure things.”

Achieving a kind of equilibrium in her eyewear is something McCartney has managed to more than pull off, with quirky geometric shapes, whimsical colors and sleek lines. “What we’re trying to do with this first collection with Luxottica is to communicate the stable message of the Stella brand, with classic pieces that you can fall back on,” she explains. “It’s the same idea as one of my coats, which are very classic with a tiny twist—something you can wear anytime. You want a pair of sunglasses that you know works for you. We’ve also got a bolder side to our brand with more statement pieces, which are a bit more attention-getting and edgy, with a kick and some humor to them as well.”

We are interrupted by a group of guests on their way out wishing to say goodbye to the designer, largely comprised of star-struck teenage girls gushing that they are huge fans of hers. “Are you going to be a fashion designer?” Stella asks one. Giddy, the girl replies that she’s torn between modeling and designing. “Well, you can do both!” Stella exclaims. “I made my first piece at 12. You can be a fashion designer and wear all your clothes. I’ll send you some fabrics to work with. You have to work with good fabrics!” One girl goes home that day a designer in the making. Maybe she will one day trace her own design inspirations to the woman who fought to claim the calling that had been rightfully hers from the start.