Facebook Messenger is now the most popular iOS app with 800 million people using it every month, according to Nielsen. App Annie revealed that Messenger is the fastest growing app of 2015.Further according to the data, people send more than 9.5 billion photos to friends through Messenger every month. Messenger has been downloaded by more than 1 billion times on Android, it said. The number of users has almost doubled from 500 million in November last year.Dave Marcus, Facebook head of messaging products wrote in a post, “It’s a good number, but we believe we have so much more opportunity ahead of us, and these are still the early days of Messenger.” “The Messenger team’s mission is to make Messenger the best place to communicate with all the people and businesses in the world,” he added. Marcus also shared that the test of M, Messenger’s digital virtual assistant, which is powered by AI, is going well. He has hinted at several other innovations to look out for in 2016. “The whole Messenger team is excited about the year ahead, and as the year goes by, about unveiling what we have in store for you. We hope you’ll enjoy these improvements,” he said.Messenger added a couple of things in 2015 including video calling, the ability to customize conversations with colors, nicknames and emojis, and with Businesses on Messenger.