Facebook invested heavily in its Messenger platform over the course of 2015 and it has become clear that the time and effort spent has paid off.

Facebook's VP of Messaging Products, David Marcus, revealed on Thursday that Messenger crossed the 800 million active monthly user milestone near the end of last year. That's more than rivals Snapchat and Viber but still shy of WhatsApp's 900 million active monthly users (not that it really matters all that much considering Facebook owns WhatsApp).

According to research firm Nielsen, Messenger was the fastest-growing app of 2015.

In 2015, Facebook added a plethora of features to Messenger including peer-to-peer mobile payments, the ability to scan your camera roll to identify friends and free video calling capabilities, just to name a few. Facebook also started testing a virtual assistant called M that's designed to make day-to-day life a bit easier for its users.

Facebook has big plans for Messenger in 2016. In a recent interview with Reuters, Marcus said one of the things they have to work on this year is the perception or mindset that Messenger is only to speak with Facebook friends. True enough, Messenger no longer requires users to have a Facebook account.

In November, it was revealed that Facebook was testing a self-destructing message feature within its Messenger app in France. No word yet on when or if the feature will eventually find its way to all users.