You can start a video call by tapping the video icon in the top right corner of the screen within an existing Messenger conversation.
Video calling in Messenger is available for calls made from a mobile phone to another mobile phone, no matter what type of device the other person is on.
The feature is launching today for people on iOS and Android in Belgium, Canada, Croatia, Denmark, France, Greece, Ireland, Laos, Lithuania, Mexico, Nigeria, Norway, Oman, Poland, Portugal, the UK, the US and Uruguay. It will be rolled out to other regions and locales over the coming months.
We'll let you know when the update is live in the App Store. Please follow iClarified on Twitter, Facebook, Google+, or RSS for updates.