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Facebook delivered for Wall Street again — and its mobile ad business is driving the bus.

The social giant beat earnings estimates Wednesday, bringing in more than $5.7 billion in mobile advertising revenue alone. That’s bigger than Facebook’s entire business in Q3 of 2015. It also surpassed one billion “mobile only” monthly active users for the first time last quarter, which means those billion-plus users never visited Facebook on any device other than a phone.

Why does that matter? Well, it underscores what we’ve known for quite a while now, that advertisers are spending more and more on mobile advertising, and Facebook is in a unique position to collect a lot of those ad dollars. In fact, it’s one of just two businesses driving the whole industry. (Hey, Google!)

So the health of Facebook’s mobile advertising business is important. And given the growth in mobile usage and mobile ad dollars, all looks good.

Facebook reported a profit of $1.09 per share on $7.01 billion in total revenue for the quarter. Analysts were looking for profit of 97 cents on sales of $6.92 billion.

The company will hold an earnings call at 5 pm ET today to discuss the news. We’ll be listening in case we they share anything interesting.