Mark Zuckerberg today showcased the "Facebook phone" as he revealed the social networking site could now become the central feature on Android mobiles.
At a highly-anticipated event at the company's Menlo Park headquarters in California he said consumers would be offered something far more than an "ordinary app" - an entirely "new experience" called Home.
He said: "Today we are finally going to talk about that Facebook phone, or more accurately, we are going to talk about how you can turn your Android phone into a great social phone."
He added: "We are not building a phone and we are not building an operating system but we are are building something that is a whole lot deeper than an ordinary app."
Within minutes of the announcement - which arguably marks Facebook's biggest jump into the mobile market - the subject began trending on Twitter.
Wearing one of his customary hooded jumpers, Zuckerberg gave a relaxed presentation telling his audience: "We're really proud of home and we're excited to get it in your hands ... we think that this is the best version of Facebook there is."
He was joined by Peter Chou, the chief executive of handset maker HTC to reveal the companies' collaboration to produce HTC First - the only phone which will come with Facebook Home already installed.
In a short explanation of how Home would work, Zuckerberg said: "The homescreen is really the soul of your phone. You look at it about a hundred times a day.
"It sets the tone for your whole experience and we think it should be deeply personal. So today we're going to talk about this new experience for your phone.
"It's a family of apps and you can install it and it becomes the home of your phone."
In a short demonstration, Zuckerberg showed viewers how the new product would appear on the homescreen of an Android phone and offered users the "highest quality experience".
He added: "At one level, this is just the next mobile version of Facebook but at a deeper level, I think that this can start to be a change in the relationship that we have with how we use these computing devices.
"For more than 30 years computers have mostly just been about tasks and they had to be... but the modern computing device has a very different place in our lives. It's not just for productivity and business although it's great for that too. It's also for making us more connected, more social, more aware.
"And Home, by putting people first, and then apps, by flipping the order is one of many small but meaningful changes in our relationship with technology."
Home will be available for download or on the HTC model from April 12, he said.
The launch followed fervent speculation online over Facebook's announcement.
But efforts by the social media giant to keep its latest venture secret were somewhat scuppered when images were leaked onto the web, while analysts widely predicted the new product would run on Google's mobile operating system.
Paul Thompson, managing director of mobile advertising firm BlisMedia, said the social networking site's latest offering was unlikely to worry the likes of Apple or Samsung.
"Is it a game changer for Facebook? Almost certainly not," he said.
"I suspect it will appeal to the die hard FB (Facebook) addicts but do consumers really want FB content to take over their whole phone?
"What about all the other live feeds already available on your phone? What about all the other things you care about outside of FB connections?
"Why would anyone want to put a FB soul into their phone?"
He added: "Will Apple or Samsung worry? Why would they? There isn't much here despite the fanfare."
The Facebook software will see feeds from the social network appear on the home page of Android phones.
From there, users will be able to access messages, pictures and notifications, rather than going through a Facebook app.
Consumers will be able to tap on pop-up images, named chat heads, to respond to friends rather than opening up apps or scrolling though menus.
HT First will be available with EE in Britain in the summer. No details have yet been given as to its price.
Pippa Dunn, chief marketing officer at EE, said: "In combining our unique superfast network with the latest integrated Facebook experience, customers will constantly be at the centre of conversations with their friends."
Ernest Doku, telecoms expert at comparison website uSwitch.com, said the Home app would give every Android phone the potential to become a "Facebook phone" and questioned whether the product could even pose a threat to Google as the "primary port of call on a smartphone".
"As a social networking site it's essential for Facebook to be on as many devices as possible, but only Android is open enough to give the social network freedom enough to truly integrate into a smartphone to the degree that Facebook wants and needs," he said.
"Piggybacking off Android's penetration and the platform's flexibility to forge ahead in the mobile market is a shrewd move and one guaranteed to put a smile on the faces of eager investors.
"It remains to be seen whether Home will wrest control from Google in terms of being the primary port of call on a smartphone."
Stuart Miles, founder of technology and gadget site Pocket-lint, said the arrival of "Home" marked an important milestone for Facebook.
"They needed a device that they could call their own," he said.
"As a concept it has potential.
"Whether it will fly off the shelves remains to be seen, though, I don't know if that is going to happen."
The launch of the enhanced app reinforces Facebook's "mobile first" approach at a time when users increasingly monitor the social networking site from smartphones and tablets.
According to the site, more than 680 million of its one billion users now check Facebook from mobile devices.
Last year, Zuckerberg pocketed more than a billion US dollars (£630 million) following its stock market flotation.
The company is now worth around 60 billion US dollars (£39.5 billion), according to the Nasdaq stock market.