The French label Sézane is known for capturing that elusive Parisian je ne sais quoi—imagine a classic Breton sweater, but with a modern silhouette and a lace collar. To Morgane Sézalory, the brand’s millennial founder, the Sézane sensibility has a depth beyond flippant French chic. “I see Sézane as a committed brand,” she says, referencing its pledge to create sustainably produced collections and a global philanthropic program called Demain, which aims to foster equal opportunities for children, as well as increase access to education and culture.

Artfully arranged goods at Le Grand Appartement, in Paris.

Before there was any brand to commit to anything, Sézalory got her start in fashion by selling her sister’s discarded clothes on eBay. She soon found herself scouring thrift shops across Paris for vintage items, then flipping her finds on the auction site. She would tweak the clothes with her own touch, hemming this and replacing the buttons on that. When her following outgrew eBay, she started her own digital thrift shop, then moved on to the direct-to-consumer retail site Sézane, which features her own designs. Her pieces are well priced and stylish, but not deliberately trendy; the mindset is conscientious, sourcing materials from labels with environmentally friendlier practices. Sézalory embraces the “Buy less, buy better” mantra. On the Web site, high-demand items often sell out—part of Sézalory’s commitment to avoid overproduction by creating limited product runs.