Venture capitalists invest in companies in search of breakout hits that attract millions of users, billions in sales and enormous valuations. These rarities, called unicorns, have grown in size and number as investors chasing returns have bid up their value. More than 70 technology companies are now valued at $1 billion or more, and the number is growing quickly. Several of the best-known Silicon Valley companies listed below are worth over $10 billion.
a mythical animal typically represented as a horse with a single straight horn projecting from its forehead.