In that time, Facebook’s revenue grew by 51%. For that, the company can thank an astonishing transition to mobile advertising. When Facebook went public in 2012, it was already late to mobile. Investors criticized the company for a missed bet that the mobile Web would trump apps. At the time of its IPO, the company had made no revenue from mobile. Even though the company was profitable at the time of its IPO, investors were hesitant because of this mobile problem.

Facebook aggressively improved its mobile app and and even more aggressively sold ads for that improved platform. Now, Facebook’s mobile advertising makes up 76% of its total revenue. The social network dominates the mobile advertising category, trumping even Google in market share, according to eMarketer.

The company’s fast growth is no surprise to shareholders. Facebook stock has risen 150% in three years, trading recently around $95 per share, with a price-to-earnings ratio of nearly 100, which is rich, even for a fast-growing tech company.

The site’s loyal audience of 1.5 billion monthly active users won’t grow forever. But to add more users, the company is targeting people who currently have no internet access by spearheading a project, Internet.org, which aims to bring internet access to remote parts of the world.

For Facebook to continue growing revenue at the current pace, it needs to sell ads that cost more. Thus, its recent push into video ads, which command a premium over regular display ad.

The company also must begin to monetize its big acquisitions: Instagram, WhatsApp, and Oculus VR, as well as Facebook Messenger. Besides Oculus VR, which won’t begin shipping virtual reality Oculus Rift headsets until sometime next year, each of Facebook’s subsidiaries has its own massive audience. While stressing that it’s still “early,” the company recently revealed plans for making money from those divisions and has been increasing ads in Instagram feeds.

Read the full list of Fortune‘s 100 Fastest Growing Companies.