Aditya Agarwal, one of Facebook's earliest engineers, revealed how Mark Zuckerberg pushed him to build a search engine for Facebook. Aditya recalled telling Zuckerberg he didn't know how to build one and suggested hiring someone from Yahoo or Google. "He's (Zuckerberg) like, 'Dude, if I can build Facebook you can build a damn search engine' and I did," Aditya said.