how did 23 years old boy build Facebook?

Facebook is one of the most famous social network sites in the world. Most of us use this site everyday . We can communicate with each other and share videos , photos and so on. Mark Zuckerberg is a ceo of Facebook . He is 23 years old and he dropped out of harvard university. A main question is how he could create Facebook with good imagination in minds of users all over the world?

Please leave your comments .Let others know what did Facebook do.

       best wishes

Seyed Babak Hosseini