Slack is a workplace messaging platform that allows users to communicate with co-workers across the country, share files instantaneously and react to news about free doughnuts with the perfect GIF. Since its launch in 2013, it’s been popularized in workplaces around the country and around the world. Slack boasts 10 million users and went public in a direct listing on the New York Stock Exchange earlier this summer. Things get philosophical as we talked with Stewart Butterfield, Slack’s co-founder and CEO, about what his company does, the future of email and how technology changes human behavior.