The 12 Best-Funded Startups You Probably Never Heard Of

Before a startup has a product ready to sell, it usually keeps its mouth shut about what it's working on. In the tech industry, that's called "stealth mode."

Most startups either bootstrap or live on a small seed investment while in stealth mode. They use that time to build the product, get some beta testers, and make a business case. They take all of that to the venture capitalists to raise the funds they need to operate.

But some startups are able to raise huge amounts of cash while still underground.

The folks at CB Insights, which collects data on venture funding startups, recently sifted through its massive database to find the most well-funded startups still in stealth mode.