Allbirds is an ecological shoe brand from California which uses wool and tree fibre instead of leather.
The company sold a million pairs within two years of launching. But even while business was booming, the two founding partners realised their relationship was in crisis.
Co-founder Joey Zwillinger discovered that working on the partnership was as important as working on his marriage.
Video journalist: Jeremy Howell
See more at CEO Secrets.
Founder of ecological shoe brand Allbirds, Joey Zwillinger, says he treats his business partnership like his marriage.