There is no sign at the building entrance, and no sign on the door of its office, either. WhatsApp is located in Mountain View - that is as much as the website will say incidentally these days the site also includes the following message in small type: 'Congratulations to Spain for winning Euro 2012!!!'. It is available for iPhone, Blackberry, Windows Phone, Android and Symbian (Nokia's operating system) and it is not limited to text messages users can send videos, photos and voice messages as well, at no cost except for an annual fee of one dollar (0.79 euros). This mobile messaging application saw the light in August 2009, and since then has been downloaded 50 million times from Google's Play store. If you carry a smartphone around in your pocket, there us a good chance that you no longer send SMS text messages, but use WhatsApp instead.

Asked about their lives, they say they would rather 'keep a low media profile, as a business and as individuals.' 'We're not a huge corporation with thousands of workers,' exclaims Koum. In fact, they guard their privacy so jealously that it is almost unnatural. Jan Koum, 36, a Ukranian, and Brian Acton, 40, an American, will reveal nothing about themselves except what's on their website, namely that 'WhatsApp was founded by two guys who spent a combined 20 years doing geeky stuff at Yahoo! Inc. This is the general headquarters of WhatsApp, one of the world's most popular applications for smartphones. 'You're the first journalist to come in here,' they say by way of welcome. Both are walking around in bermudas and a t-shirt. A view of the WhatsApp headquarters in Mountain View, California.

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