If you haven’t heard of Slack, it’s the new runaway success of Flickr founder Stewart Butterfield. 

It’s software that allows groups to work better together. But unlike the disappointing such tools that have come before it, Slack is brilliantly designed and beautiful to use. In under two years it’s gone from nothing to a $1B valuation and 30,000 companies as customers.

This fantastic piece from VC company First Round looks at how.