Facebook is rolling out a new app, Messenger Kids. It's coming out as a limited preview on Apple devices in the United States. Facebook's app is designed for users under the age of 13. It lets them do video chats and send photos, videos and texts. But first, kids must get a parental approval. Parents use their Facebook email and password to activate their child's account. They also have control over their kid's online activities. Facebook says the app won't display ads. And the company won't mine data from it.