Facebook launched its new Android "experience", Facebook Home, with a messaging feature called Chat Heads at its heart. When a user's Facebook friends start a new chat, their picture pops up on Android phone home page in a small bubble – a "chat head".
"We think that Chat Heads are this great, personal way to do messaging," said Facebook CEO Mark Zuckerberg at the presentation in San Francisco, California. Adam Mosseri, Facebook product designer, said the feature would personalise people's phones better. "What we're trying to do is shift people's focus away from tasks and apps and toward people," he said,
He demonstrated how the phone bounces back and forth between the various features. "There's nothing between you and your content. You can literally just reach out and touch it," Mosseri says. If you can't quite picture Chat Heads, imagine if the text message bubble on your phone expanded and saturated everything, everyone in your contacts grew a bubble head, and whenever you revved up your phone, your friends' heads would be there, talking to you.
Source: https://www.guardian.co.uk/technology/2013/apr/04/facebook-home-chat-heads-messaging?INTCMP=SRCH