Today Facebook will sell shares in one of the biggest tech IPOs in history. New investors will gobble up the stock to get a piece of the global phenomenon famously started in Mark Zuckerberg’s dorm room in 2004. But while owning the stock will have quantifiable value when it trades on the open market, few buyers will be able to say truthfully that they understood the value of the company just a few years ago.

Ask yourself candidly, what did you think of Facebook the first time you landed on its homepage? Were you blown away? Could you see how it would fill a gaping need in the lives of nearly a billion people? If you’re honest with yourself, and you’re not Peter Thiel, your answer is probably, “No, not really.”

Don’t feel bad. Like many of the astoundingly successful web companies of the last decade, it was hard to appreciate the value of Facebook at first glance. But one person who “got Facebook” early on was Noah Kagan, who in October of 2005 joined the company as one of its first product managers. In 2006, Noah was the source for an analysis of Facebook written by Nisan Gabbay. The essay identified one of the most important reasons for the company’s ascent to Internet glory and offers a prescient description of opportunities still to come:

“The Facebook success story is most interesting to me because of how daily offline social behavior drove usage of the site. There are plenty of activities in our daily life that could benefit from a complementary online product … Facebook demonstrates you have a great Internet service if offline behaviors can drive nearly daily usage online.”

The analysis was spot on. Facebook succeeded because it built new online habits around frequent offline behaviors. Originally, Facebook was designed to replace the physical face books undergraduates received their first week of school. The printed collection of classmates’ names and photographs was an indispensable artifact of college life and was referenced for everything from study group formation to late-night hookups.

TheFacebook.com, as it was originally known, offered users a digital way to feel connected to others throughout the day and from anywhere they could access the web. The power of this universal human need for social acceptance and connection helps explain how the company grew well beyond college campuses and now touches one in eight people on the planet.