(ABC NEWS) Mark Zuckerberg, CEO and founder of Facebook, and COO Sheryl Sandberg gathered with a throng of cheering employees at the company headquarters in Menlo Park, Calif., to ring the Nasdaq’s opening bell ahead of the social media network’s long-awaited IPO.

With a large monitor and stage set up outdoors, instead of visiting Nasdaq’s New York exchange, hundreds of employees gathered in the early hours of the morning in California. Many of them had participated in Facebook’s “hackathon,” a company tradition described as an overnight sleepover that encourages employees to work on anything but their normal work duties.

Nasdaq’s CEO, Bob Greifeld, stood beaming next to Zuckerberg, clapping along with the other employees.

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