As confirmed in an email from an Instagram spokesperson, it's super easy to connect your two accounts, and completely opt-in. Simply launch Facebook Messenger, tap on the People tab and then hit "Connect to Instagram." You'll then tap a button to connect to your Instagram account, which will find all your mutual Messenger contacts from the photo-sharing service. The app will offer the option to start conversations with those people, or you can skip it and just get back into Messenger proper.

Allowing the more than 700 million people who use Instagram (as of last April) easy access to Messenger is a no brainer for Facebook, as it continues to bring it's two hot social properties together on your phone.