Here is a brief excerpt from an article by Erin Griffith for FORTUNE magazine in which she observes that the billion-dollar tech startup was supposed to be the stuff of myth. Now they seem to be…everywhere. To read the complete article, check out others, and obtain subscription information, please click here.

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Stewart Butterfield had one objective when he set out to raise money for his startup last fall: a billion dollars or nothing. If he couldn’t reach a $1 billion valuation for Slack, his San Francisco business software company, he wouldn’t bother. Slack was hardly starving for cash. It was a rocket ship, with thousands of people signing up for its workplace collaboration tools each week. What Slack needed, Butterfield believed, was the cachet of the billion-dollar mark.

“Yes, it’s arbitrary because it’s a big round number,” says Butterfield, 41. “It does make a difference psychologically. One billion is better than $800 million because it’s the psychological threshold for potential customers, employees, and the press.”

Sure enough, in October—less than a year after the company released its namesake product—Slack announced the close of a $120 million round of financing. Its valuation? One billion dollars. Butterfield’s wish had come true: Slack was the tech world’s newest “unicorn.”

It wasn’t long ago that the idea of a pre-IPO tech startup with a $1 billion market value was a fantasy. Google was never worth $1 billion as a private company. Neither was Amazon nor any other alumnus of the original dotcom class.

Illustration by Jeremy Enecio for FORTUNE

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Here is a direct link to the complete article.