Just days after Mary-Kate and Ashley Olsen opened the doors of their first-ever, brick-and-mortar Elizabeth and James store at the Grove in Los Angeles, InStyle celebrated the launch with the famed twin designers via a star-studded bash inside Chateau Marmont’s Penthouse. The ladies of honor, who made a rare public appearance for the Tuesday evening fête, were accompanied by Mary-Kate’s husband, Olivier Sarkozy, as they greeted guests with hugs and smiles. Keeping in line with their signature, effortlessly chic style, both Mary-Kate and Ashley donned ankle-length coats, with Mary-Kate wearing a sleek black trench with rolled up sleeves paired with a textured oxblood Elizabeth and James handbag and multi-colored bracelets. Ashley contrasted her sister’s look in an off-white belted Elizabeth and James coat paired with a brown clutch. The duo’s younger sister, Elizabeth Olsen, was also on hand to support her siblings, telling InStyle, she was thrilled to be there. “Anything to celebrate how smart and talented and great my sisters are, I’m there very, very quickly,” the actress, who wore Elizabeth and James jeans, along with an Elizabeth and James jacket, bracelet, bag and satin Manolo Blahnik pumps, told InStyle. “I’m so inspired by everything they do and their work ethic and their eye. I’m always excited to celebrate.” Guests at the event enjoyed stunning views of the city, as they walked past mirrored tables topped with fresh flowers and clustered glass votive holders flickering with candlelight. The vibe was casual L.A. chic, with the fashionable attendees opting for Elizabeth and James pieces and understated designer garments for the bash. They sipped signature “Elizabeth” and “James” cocktails and Rouge bourbon iced tea, and munched on an assortment of small bites, including bacon wrapped dates and avocado toast, with Elizabeth grabbing a bite of the latter. As the night went on, guests gathered outside by candlelight, mixing and mingling along the patio. Christina Hendricks, who attended the event with her husband Geoffrey Arend, sat on a bench and caught up with a couple of girlfriends. The former Mad Men star remarked that she’s been a "huge, longtime fan" of Mary-Kate and Ashley, with whom she chatted earlier in the night. “I think they're style icons,” she told InStyle. “I just think they always look amazing. I’m always admiring them.” Heidi Klum, who sported a pink Elizabeth and James dress, echoed those sentiments. “I love their clothes. I mean, I really do. I love The Row. I love Elizabeth and James," she told us. "I don’t really buy a lot of things. But, what I will buy is Elizabeth and James or The Row. I just feel like they always get it kind of right.” Meanwhile Pretty Little Liars star Lucy Hale told us she loved the “intimate vibe” of the event, and her co-star Shay Mitchell said she was happy to enjoy a “cold glass of wine” after enduring the 90 plus temps in the city for the last week. It was not only a night to celebrate fashion, but a chance to relax and release with friends as well. Scroll down for an intimate look at the evening.