Mobile phones are the defining technology of the 21st century, changing people's daily lives across the globe, and, since 2006, Barcelona has hosted the mobile industry's most important event. It's an exhibition and also a conference, at which mobile operators, tech companies and manufacturers come together. With presentations of all kinds of new devices, the congress is about much more than phones - last year, virtual reality headsets from Samsung and Oculus, HTC and Valve were among the gadgets that generated most buzz. The four-day conference programme looks to the future with keynote speakers that have included top tech names such as Facebook's Mark Zuckerberg. In 2015, there were 94,000 attendees from 201 countries, making it the biggest yet.