Facebook IPO: 1-Year Anniversary Photos Facebook IPO: Social Network's Timeline Facebook became a publicly traded company on the Nasdaq May 18, 2012. Founder Mark Zuckerberg and COO Sheryl Sandberg ring the Nasdaq opening bell. Facebook History It all started here. Mark Zuckerberg and three friends created Facebook in his Harvard dorm in 2004. Bill Greene/The Boston Globe via Getty Images Mark Zuckerberg, the founder of Facebook, wearing a hooded sweatshirt. It would become his signature look. Mark Zuckerberg Eduardo Saverin was one of the four co-founders of Facebook. He and Zuckerberg parted ways early in the company's history, though he remained a shareholder and the company's IPO is reported to have made him a billionaire. Gilbert Carrasquillo/FilmMagic One of the first Facebook interfaces. The social network was originally just for college students. In 2006, Facebook opened its doors to all. The Winkelvoss twins, Cameron and Tyler, accused Zuckerberg of stealing their idea to build a social network for Harvard students. The Winkelvoss twins eventually settled with Facebook. Jonathan Ferrey/Getty Images Facebook went from a small start-up to one of the largest in Silicon Valley. Here employees work at Facebook headquarters in 2009. The company has since moved to larger quarters. Tony Avelar/Bloomberg via Getty Images Zuckerberg grew up, and so did the site. Here Zuckerberg delivers a keynote to hundreds of Facebook developers and media at the annual f8 conference. Kimihiro Hoshino / AFP / Getty Images The announcement of Open Graph was a turning point for Facebook. It allowed other websites and apps to tap into Facebook, allowing "liking" on other websites and different devices, and spreading Facebook's online presence. Justin Sullivan/Getty Images Maybe, just maybe, Facebook really arrived when a feature film was made about it. "The Social Network," with a screenplay by Aaron Sorkin, premiered in 2010. Columbia Pictures Zuckberg introduced the biggest change to Facebook in 2011 - the Timeline. The new profile layout displays a user's history chronologically, back to your date of birth if you so choose. Facebook snatched up small companies along the way, but the biggest came in April 2011. It bought Instagram, a photo sharing app, for $1 billion. Facebook founder and CEO Mark Zuckerberg and Priscilla Chan are shown at their wedding ceremony in Palo Alto, Calif., Saturday, May 19, 2012. Zuckerberg updated his status to "married" on Saturday. The ceremony took place in Zuckerberg's backyard before fewer than 100 guests, who all thought they were there to celebrate Chan's graduation. Allyson Magda Photography, Facebook/AP Photo Facebook's Social Timeline Facebook's Graph Search, released in in March 2013, allows you to search more about your friends, including their interests and photos. Michael Goodwin displays an HTC First cellphone with the new Facebook interface at Facebook headquarters in Menlo Park, Calif., April 4, 2013. Facebook released its Facebook Home software, which replaces Google?s Android homescreen with Facebook photos and updates. Marcio Jose Sanchez/AP Photo Facebook CEO Mark Zuckerberg speaks at the company's headquarters in Menlo Park, Calif., April 4, 2013. Zuckerberg says the company is not building a phone or an operating system. Rather, Facebook is introducing a new experience for Android phones.