Remember when Facebook made you download a new app called Messenger? Well, as of Tuesday that app, which split off instant messaging from Facebook, crossed 1 billion downloads on the Google Play store, putting it in a very elite group.

Only Facebook's and Google's app have reached this milestone on Android. The other apps that have made the grade are Facebook (as of September 2014), Facebook-owned WhatsApp (as of March 2015) and Google's standalone search app, Gmail, Maps and YouTube. Many of Google's apps come pre-installed on Android devices. 

In April 2014, Facebook began to require all users to install Messenger in order to use messaging via the site on their smartphones. With the Facebook app reaching 1 billion installs on the Google Play store in September 2014, the milestone was anticipated, but nevertheless gladly embraced by the social network's executive team.

facebook messenger David Marcus, Facebook's vice president of messaging products, shared the milestone for Messenger downloads on Google Play on his Facebook Timeline on June 9, 2015. Facebook CEO Mark Zuckerberg 'liked' the status update. Photo: Facebook Screenshot

Just because Messenger has been downloaded 1 billion times doesn't mean 1 billion people are actively engaging with it. Facebook has repeatedly said that Messenger has 600 million monthly active users. That number stretches across the app's availability on iOS, Android, Windows and on desktop. The social network's site reportedly has 1.44 billion monthly users -- so that's 41 percent of Facebook's total active users also engaging with Messenger.

Facebook has continued to make its messaging app more attractive to users. In March 2015, it opened Messenger to third-party apps, allowing users to send videos, songs and other enriching -- or ridiculous -- experiences. Just last week, Facebook added integration with Apple Maps and Nokia Here that allows users to send maps of their locations. Facebook is also testing payment sending through Messenger and business-to-customer communication.