New Zealander and former pro soccer player Tim Brown hung up his cleats in 2010 after going to the World Cup. His next move surprised everyone: He set out to make simple shoes that looked nothing like the ones he was paid to wear as an athlete. He teamed up with biotech veteran Joey Zwillinger to re-engineer the running shoe out of wool. Here, Brown and Zwillinger describe how, after eight years and many prototypes, Allbirds has become a cult brand--especially in Silicon Valley--by keeping things simple. --As told to Lindsay Blakely

Tim Brown: Part of my job as a pro soccer player was to wear sponsored sportswear and footwear from the big apparel companies. My initial insight was that footwear had become overdesigned, over-logoed, overly bright--and you're overwhelmed by the amount of choice. So the early idea was: make a very simple silhouette--the simplest sneaker that you possibly could.

I found a factory literally on the internet while I was still playing. Going into my first factory led to insight No. 2: footwear is old-fashioned industry that is very cost conscious, so it tends to default to cheap materials and less-than-thoughtful manufacturing. The innovation alarm went off. There was a huge unexplored opportunity in natural, sustainable materials starting with wool, which is abundant in New Zealand. With a grant from a New Zealand farm funding body, I developed the first textile but I had no sense of how hard this would be to pull off.

Joey Zwillinger: We became friends through our wives. We started talking and I realized the opportunity is bigger than wool and it's bigger than shoes. It's really about sustainable materials that people have overlooked and using them to make amazing products--not just for the sake of making them sustainable but to make amazing products full stop.

Brown: Everything we do is about simplicity. We like to say that we want to design the right amount of nothing in our shoes. We also launched with only one shoe style direct to the consumer, which by the way, is absolutely not how you launch a shoe brand. Even some of our investors started to question our approach. You're supposed to launch with a range of styles and change them every season. There is this misconception that innovation is about adding bells and whistles and making something shinier and brighter. But often it's about stripping everything away. The irony is doing something simply is incredibly hard. When you're taking away everything, there's a focus on form and there's nowhere to hide, so you have to get the silhouette right. It was an exhausting process--and it wasn't right up until it was right.

Zwillinger: There were a lot of moments of doubt. It became not just about how to launch a shoe company but also about how to launch an e-commerce company. We said no to things like offering people a discount in exchange for their email address. People said that's the way to do e-commerce because then you can spam customers later and try to sell them things they didn't really want. We said no to selling the shoes wholesale--we wanted to have a direct relationship with consumers. We said no to coming out with a line of shoes instead of a single shoe. It was very unnerving to hear we were doing it the wrong way from so many people. But we had a lot of conviction that doing less would allow us to do more and to break through to the consumer.

Brown: We're able to stay tightly focused because we make decisions based on three things: comfort, simple design, and a laser focus on sustainable materials. At one point we were incredibly frustrated because we wanted to create a textured shoelace using post-consumer materials and we couldn't figure out how to do it. Our manufacturer finally came to us and said they had found a way to make a pair of laces from a plastic bottle, but it was going to cost twice as much as standard laces. 

Zwillinger: We got everyone together--product people, marketing people, our CFO, who's obviously in charge of watching our margins. The meeting lasted literally less than a minute--everyone was 100 percent on board. The CFO said, "yeah, this is a no-brainer." We can make consensus decisions like that because our vision is clear and uncluttered with distractions.

Brown: This focus just isn't going to change. It took us over a year to launch a second style. Another year passed before we came out with our eucalyptus pulp shoe, the Tree Runner, which was a response to consumer feedback about wanting a warmer weather shoe. You can already see from that cadence it's been incredibly deliberate. That discipline has been a key part of our success and we don't want to lose it. 

From the July/August 2018 issue of Inc. Magazine