How many zeroes would you expect to find in a 25-year-old’s net worth? If you said nine, you’re probably thinking of Mark Zuckerberg, the man behind one of the Internet’s prized distractions: Facebook. Zuckerberg is current the 158th richest person on the Forbes 400 list with $2,000 million in assets.

Like so many billionaires, Zuckerberg had excellent educational opportunities, attending Phillips Exeter Academy for high school and Harvard University for undergrad. And like so many billionaires, Zuckerberg left college degree-less so as to earn his fortune; after launching and maintaining Facebook from his dorm room, Zuckerberg moved to Palo Alto between semesters with some friends… and stayed there.

So, what’s the secret to his success?

It really started with a great idea. Why not take something people already know, a yearbook, and make it digital? (At Zuckerberg’s alma mater Exeter, they even used to call the school yearbook the “Facebook.”)

We’re approaching Facebook’s six year anniversary, and even with all the features that have been added over the years—feeds, statuses, notes, fan pages, and applications, not to mention support for non-collegians—the website maintains its core identity as a powerful networking tool, a digital yearbook.