Fabric may seem like an obvious factor in fashion, but for designer Anne Fontaine it’s the inspiration. “I am obsessed with natural textures,” she said. “I love fabrics, and I want to work with natural fabrics.”

But make no mistake: She’s not talking about hemp shoes with burlap trim. Since she opened her first shop in 1994, Anne Fontaine’s stock-in-trade has been luxurious white shirts for women. They may range from frilly to simple, but they always convey elegance without pretension.

Tonight, Ms. Fontaine will inaugurate her flagship store on Madison Avenue — just a few doors south of the former shop. Designed by the celebrated Andrée Putman, The three-story shop boasts 7,500 square feet and immediately gives the visitor the sense that fabric is important here: the glass windows are printed with flowing lines that mimic the woven threads of fabric. Exclusive to New York is a room painted black and lined with a collection of near-couture pieces in exquisite fabrics with hand-stitched embellishments. Two V.I.P rooms are available for private, by-appiontment shopping — and special iPod ports allow the client to shop to her own tunes.

But the space is not intended for retail exclusively. Ms. Fontaine plans to launch a spa on the third floor by 2009. And if the spa in her shop on the Rue St. Honoré is any evidence, the Madison Avenue version will be one of Manhattan’s premier destinations for an in-town getaway.

While the combination of shirts and spa treatments might seem incongruous, listening to Ms. Fontaine describe her work puts it all in context. In the last few years, the Anne Fontaine brand has been expanding into jewelry, accessories, and home fragrances. And for this Brazilian-born designer, health and beauty is a logical extension of the lifestyle she wants to encourage: joy derived from simplicity and an appreciation for nature. “People are so stressed. It’s important to take time for yourself, to protect your life,” she said.

At the Paris spa, which is located one story below the retail shop, Ms. Fontaine’s devotion to natural fabrics runs strong. The heavy doors that separate the waiting room from the interior treatment rooms contain a thin sheet of organza pressed between two plates of thick glass. The white walls are covered in canvas imprinted with the pattern from a piece of tulle. And while some treatments are inspired by scents (such as the Doce de Leite Body Scrub) or by specific needs (such as the time-zone-blurring Anti-Jet Lag Massage), many give a nod to fabrics. The process of silk weaving inspired the technique used for the Sensory Draining Massage, and cottonseed oil is incorporated into the Relaxing Full-Body Massage.

When it’s time to come in contact with actual fabrics, such as towels and robes, there is a strong temptation never to leave this immaculate wonderland. Even the disposable undergarments provided to guests are noteworthy: Instead of gauze held up with a thin elastic band, a white lace thong is placed on the guest’s massage table.

Although the New York version will also be designed by Ms. Putman, it will stand on its own. “I want every flagship to be different,” Ms. Fontaine said.

Even so, the mood will connect to the Anne Fontaine sensibility. A tall, model-like woman with long brown hair, Ms. Fontaine lives in Honfleur, Normandy, with her husband Ari Zlotkin and two daughters, ages 9 and 3. How she balances her time between her family, herself, and the 70 stores around the world — including the first concept store containing a spa, which she launched in Tokyo — is simple, she says: “It’s all about organization. It’s all in my head, the next 24 hours.”

Ms. Fontaine first went to Paris to study. “I wanted to be a biologist,” she said. Her plans changed after meeting the man whom she would marry. His family owned a factory that specialized in making shirts, and together they developed a business around designing white shirts for women. At age 22, she designed her first collection.

With the spa, the designer returns to her interest in biology. Not only has she created a space that frees the mind to engage with the senses, but she has overseen the production of a line of eponymous face, body, and hair care products. Made in the South of France, the products were developed with the fabric theme in mind: the Natural du Lin items were derived from linen seed and lilac, while the Performance de Soie group is based on silk.

One of Ms. Fontaine’s most important goals was to give the scents an unmistakable, alluring fragrance. Indeed, the linen-inspired products are scented with all-natural flower essences, including orange and mandarin blossom, geranium, and lavender. “Scent is such an important sense. You can develop it like you learn to read and write,” she said.

In Anne Fontaine’s world, scent can float by as you’re being massaged while a fine mist of water is released above you — or while you’re relaxing after the massage with a cup of birch tea. It can happen in Paris, Tokyo, or New York. Whichever way, the scents will build a memory to last.

(Anne Fontaine, 677 Madison Ave., between 61st and 62nd streets, annefontaine.com)