These 16 startups are worth $22 billion: Here are the deals that made them so valuable

Last week, news broke that Slack was raising a new round of investment that would value the young company at a jaw-dropping $2.76 billion.

That would make Slack the second most valuable enterprise startup in the world, according to valuation expert PitchBook. (By "enterprise startup" we mean a company that primarily sells tech to businesses as opposed to consumers.)

We asked PitchBook to send us a full list of the most valuable enterprise startups in the world, along with details from public filings on the investments.