If all you know of Allbirds is that it is a Millennial-cool sneaker company that periodically serves you timely advertising for its eco-friendly products, that’s fine: through that direct-to-consumer communication, Allbirds has become a unicorn, valued at more than $US1 billion ($1.45 bllion) with combined funding of $US150 million.

Now the brand, co-founded by New Zealander Tim Brown, is ready to make the leap into apparel, betting on the idea that if people like its all-wool sneakers so much, they might just like its eco-friendly underwear, too.