Unicorns. That term has been mentioned ad nauseam in the press in recent years, as private companies see their valuations swell due to a number of factors, including central banks around the world providing copious amounts of liquidity, a resurgent global economy and a number of disruptive technologies converging at once.

While the so-called unicorn needs to have a valuation of $1 billion or more, the list keeps growing and shows no sign of slowing down.

According to data compiled by research firm CBInsights, there are now 202 so-called unicorn companies, with a collective valuation of $690 billion. The industries these companies touch are as diverse as ever, including common ones such as social networking and e-commerce, but expanding into areas like health insurance and even the fitness equipment industry. 

The vast number of these companies have been founded in the past decade, but the list has grown significantly in the past five years. "Firms founded from 2012 to 2015 had a time to market cap more than twice that of firms founded from 2000 to 2003," according to a report in the Harvard Business Review. This means that start-ups founded in the past five years are growing at a rate twice as fast as those that were started a decade ago.

There has been some concern about which of these companies are able to generate meaningful revenue and how they would fare on the public markets. However, there's no denying that companies like Uber, Pinterest, SpaceX and others have changed our world forever, even if the average investor still can't own shares yet.

What's Hot on TheStreet

Respect the stock charts: Don't feel too relieved by volatile tech name Nvidia (NVDA) - Get Report finishing in the green on Monday after a violent selloff.

Nvidia underwent a "key reversal" on Friday that could send the stock plunging another 36%, BMO technical analyst Russ Visch said in a new note. Visch points out that normally, these pullbacks tend to lead to the stock falling back to its 200-day moving average. In the case of Nvidia, the 200-day moving average is $96.70, or $36% below Monday's closing price of $149.97. "Considerable downside risk exists here," said Visch.

On Friday, shares of Nvidia were off to another big rally, hitting new all-time highs of $168.50 following an analyst pontificating the stock could surge to $300. But the party abruptly ended Friday afternoon and continued into most of Monday's trading session. The reversal in one of the hottest tech stocks around spooked the market, pressuring shares of other high-flyers in the space such as Amazon (AMZN) - Get Report and Apple (AAPL) - Get Report .

Apple and innovation: The reality of the here and now is that the public and would-be buyers of Apple's stock harbor greater doubts about Apple's ability to innovate than in many years, reportsTheStreet. Apple did nothing to quiet those concerns by introducing its new voice activated speaker, sources explained to TheStreet.

Yet another Tesla bull: A new day, yet another Wall Street firm with some bold proclamations on electric car maker Tesla (TSLA) - Get Report . Tesla shares were upgraded to buy from hold on Tuesday by Berenberg, citing the company's "disruptive potential" in the auto industry. The company could have a "near monopolistic" opportunity to gain market share and out-perform rivals, Berenberg writes.

The firm sees Tesla shares surging about 30% from Monday's closing price to $464.

Sears' demise continues: Sears Canada said Tuesday that cash flows from sales "are not expected to be sufficient to meet obligations coming due over the next 12 months," after reporting a first quarter loss. Meanwhile, Sears Holdings Corp. (SHLD) also had more worrying news.

Apple is a holding in Jim Cramer'sAction Alerts PLUS Charitable Trust Portfolio. Want to be alerted before Cramer buys or sells AAPL? Learn more now.

With help from CBInsights, here are the ten largest private companies in the world.