Behind that success? Celebrities—but not in the way you’d think, Emily Weiss, Glossier’s founder and CEO, explained at Fortune’s Most Powerful Women Next Gen conference Tuesday in Laguna Niguel, Calif.

When Glossier sought to create a new facial cleanser, it wanted to know what its customers’ ideal product would be. In order to find out, Glossier asked, “What would be your dream face wash…who would play it in a movie?” Weiss said.

The answers included Eddie Redmayne, the Oscar-winning actor who starred in the films The Theory of Everything and The Danish Girl; Julianne Moore, and Emma Stone. Weiss and her team were quick to spot the pattern: “All redheads,” she observed.

Glossier’s takeaway: Consumers wanted a face wash made for lighter, perhaps more sensitive skin, and the company set about making it. The result is Glossier’s Milky Jelly Cleanser, “which is now a best seller,” Weiss noted.

Listening to what customers’ want has been the driving force on the journey to $100 million in sales, she said. “We’re just obsessed with customers…We’re obsessed with including her. And we actually co-created a lot of products with her,” she added, referring to their target female shopper.

At the same time, Glossier has eschewed celebrity spokespeople and avoiding paying Instagram “influencers” to promote products, preferring instead to rely on customers to spread the word. “We’ve always been pretty adamant that everyone with an Instagram account is influential,” Weiss said. To that end, Glossier responds to all the direct messages it receives on Instagram—which arrive at a rate of five per minute.

There was one instance, however, when Weiss did consider hiring a celebrity. “I did ask a friend of a friend, you know, would Eddie Redmayne be available to talk about this face wash?” she said. “Obviously the answer was no.”