Slack’s explosive word-of-mouth growth in one amazing chart

Slack, a year-old chat tool designed for companies and work teams, just soared past 100,000 daily active users. And that’s without spending any money on ads, according to a recent Wired profile.

This growth chart, tweeted today by Slack investor Marc Andreessen, is most impressive. It’s too early to tell if Slack—or any other tool—will supplant email for most online business communication. But Slack’s explosive growth so far suggests it’s doing something right.