Facebook Messenger has now reached heights few mobile apps dare to dream of: It has more than one billion monthly users.

With this accomplishment, Messenger finally joins the vaunted ranks of Facebook's primary app and WhatsApp, both of which also count more than one billion monthly active users. The milestone comes nearly five years after the launch of the mobile app, which crossed the one-billion mark in late June.

Since  spinning Messenger out of its primary app in early 2014, Facebook has been busy adding countless features to the messaging tool. These days Messenger does much more than one-to-one communication. Users can make audio calls, send stickers, chat with nifty bots, or simply send their friends giant blue thumbs. As a result, Messenger has managed to rack up more than 700 million users in the past two years alone.

Facebook timed its big announcement exactly one week before the company delivers its latest quarterly earnings. Messenger's feat comes about one month after Instagram hit a major milestone of its own, crossing the 500-million-user mark.

Altogether this should please shareholders, but despite all these new users, one major question remains: How will Facebook monetize Messenger? Facebook has toyed with ideas here and there, such as the possibility of selling stickers to Messenger users.  Some predict that Messenger will eventually gain revenue by letting you make purchases directly from bots that can sell you goods or services. But so far, Messenger has not managed to put together any significant amount of revenue.

Fortunately for Facebook, its social network ad revenue is doing well enough on its own to take pressure off any of its other products. The hope is that eventually Messenger, WhatsApp, Instagram, and other products will contribute to Facebook's bottom line, but for the time being, Messenger and its siblings have the luxury of continuing to focus on user growth.