Mark Zuckerberg is likely lounging in a high-rise office somewhere right now, giggling gregariously. When Facebook purchased Instagram for a seemingly ridiculous $1 billion back in 2012, some scoffed at Zuckerberg's valuation of the app. Three years later, Zuckerberg is flexing unapologetically with news of Instagram recently surpassing 400 million total users.

"We are thrilled to announce that the Instagram community has grown to more than 400 million strong," Instagram said in a statement on Tuesday. "While milestones like this are important, what really excites us is the way that visual communication makes the world feel a little bit smaller to every one of us."

The most compelling fact about Instagram's latest milestone is that approximately 100 million of these users were gained in the last nine months alone, according to Forbes. These numbers also add real weight to the value of Instagram ad placement, making that aforementioned billion-dollar deal seem more and more like scoring something on the (billionaire's version of) low:

Instagram is poised to deliver a powerful shot in the arm for Facebook.  Research firm eMarketer recently estimated that Instagram’s ad revenue will reach about $1.5 billion in 2016 and $2.8 billion in 2017. This year, eMarketer forecasts Instagram’s global ad revenue will be $600 million.

Twitter currently stands tall with 316 million monthly active users, placing it nearly 100 million behind Instagram, but what's a few million users between frenemies?