15 of the fastest growing startups in the world still flying under the radar

By now, startups like Slack, MongoDB, Cloudera, Pure Storage are well known for their fast-growing businesses.

But we wondered: Who are the fastest-growing startups in the world that serve businesses, that we should be hearing about next (i.e. enterprise startups)?

That's a loaded question, we know. It all depends on your definition of "fastest growing." Startups are private companies that don't have to release their revenue numbers, so we couldn't measure them that way.

We turned to PitchBook Data, a company that monitors the public records of venture and private equity funding, to help us.