A lot has changed since Mark Zuckerberg launched TheFacebook in 2004. Here are some of the milestones that mattered most.

Elena Lacey

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On February 4, 2004, back when "Hey Ya!" was still topping the charts and global dominion was but a glimmer in a young Mark Zuckerberg’s eye, the 19-year-old Harvard sophomore and his roommates unleashed their creation, TheFacebook.com, on humanity. Or at least, they unleashed it on the elite sliver of humanity that occupies Harvard's halls.

But over the past 15 years, that sliver has expanded far beyond anyone's expectations---including Zuckerberg's. In June 2004, when WIRED published its first story on TheFacebook, comparing it to Friendster and whatever the heck Orkut was, Zuckerberg said, "I expected that a few people would do it at Harvard and they'd tell their friends, but I didn't expect it would take hold as this all-inclusive directory."

At that point, success meant having 250,000 users on the platform. In the decade and a half since, Facebook has added four zeroes to that figure, transforming from a website for poking your college crush to, arguably, the most powerful engine of communication in the world. Zuckerberg's creation has, for better and for worse, forever changed how people connect, how businesses make money, how politicians seize power, and how information flows across communities and cultures. It's where grannies share pictures of their grandkids and where state-sponsored trolls wage cyberwar against other countries. It's how volunteers raise money for hurricane victims and how hate-mongers rally their followers to kill people.

How did that happen? We took a look back at Facebook's 15 years for the 15 moments that made the company what it is today and that signaled, sooner than most realized, what it would become.

1. The Winklevii sue Facebook.

TheFacebook.com was just seven months old when ConnectU, a startup founded by Harvard students Cameron and Tyler Winklevoss and Divya Narendra, sued Facebook for breach of contract in 2004. In what would become a years-long legal battle, memorialized in the Oscar-winning film The Social Network, the ConnectU founders alleged that Zuckerberg stole their idea and breached an oral contract he made to develop a social network for Harvard students that was then called HarvardConnection.

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Zuckerberg had already launched a short-lived Hot or Not clone called FaceMash the year before. That site got him in trouble with Harvard, because the app used students' photos without their permission, but it also caught the attention of the HarvardConnection founders, who turned to Zuckerberg for help building their site. What they didn't know then---and what would later be revealed through court filings and leaked instant messages---was that, while Zuckerberg appeared to be toiling away on HarvardConnection, he was simultaneously building TheFacebook.

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The HarvardConnection team sent Zuckerberg a cease and desist letter days after TheFacebook launched and filed a formal lawsuit that September.

The bitter suit ended in a settlement. But the battle with the Winklevii provided an early look at how Facebook would come to use a combination of skill, speed, and eventually, size to copy or crush competitors.

2. News Feed launches.

In the beginning, Facebook was more or less a directory of people's profiles. Spending time there meant bouncing from one friend's Wall to the next, checking out the latest posts. The launch of News Feed in September 2006 changed that forever, creating a centralized stream on users' homepages, where they could see all of their friends' updates.

When Facebook flipped the switch on News Feed, however, users were outraged. Suddenly, every action they'd taken on Facebook was visible to all of their friends. (In my case, that meant exposing a late-night, not entirely sober decision to friend every member of the New York University men's cross-country team.) In a blog post for a proposed Facebook boycott, one user wrote, presciently, "It is almost impossible now to keep your information to yourself."

The News Feed debacle presented Facebook's first opportunity to defend itself against accusations that it had invaded users' privacy. It didn't go so well. "Calm down. Breathe. We hear you," Zuckerberg wrote in a less-than-compassionate Facebook post responding to the backlash. "Nothing you do is being broadcast; rather, it is being shared with people who care about what you do—your friends."

Days later, Zuckerberg backtracked in an open letter, saying, "We really messed this one up," and announcing new controls users would have over what stories populated their News Feeds. "When we launched News Feed and Mini-Feed we were trying to provide you with a stream of information about your social world," he wrote. "Instead, we did a bad job of explaining what the new features were and an even worse job of giving you control of them." It's the sort of apology that would become all too familiar in the years to come.