Who says teens aren’t using Facebook? Not Nicola Mendelsohn, the company’s VP of Europe, Middle East and Africa.

On Tuesday, Mendelsohn poo-pooed reports claiming the company is struggling to engage young users. “This issue of teens is just not true. We have the most engaged audience with young people on Facebook,” she told attendees of the Fortune Most Powerful Women International conference in London. Mendelsohn then cited a Forrester Research study, released today, that says three quarters of young people on the Internet use Facebook FB . “They’re spending more time on Facebook. We think this is because of the shift to mobile,” says Mendelsohn.

Which explains the social network’s recent acquisition of mobile messaging platform WhatsApp for the jaw-dropping price of $19 billion. “We want to make the world more connected,” Mendelsohn said, nodding to Facebook’s now-famous tagline. WhatsApp has over 500 million users and a large following in developing markets. Mendelsohn says that Facebook noticed that it’s “not the best user experience for people to just do everything in one place [on Facebook].” The acquisition allows the social network to branch beyond its own site. “There’s a whole new way of people communicating. [They’re] still sharing. We see that it’s mobile, and we think mobile is the platform of today.”

Facebook’s pivot toward mobile has helped spark growth in the regions Mendelsohn oversees. “It was because Mark Zuckerberg turned around and said, ‘We’ve done this wrong. We now need to go mobile first. Nobody can come in here now and show me any new products unless it’s on mobile,'” says Mendelsohn. “The growth of mobile has taken everybody by surprise.” Facebook now has over a billion people using Facebook on mobile every month, she added–and about three quarters of that billion are coming back daily.

Facebook may think mobile’s the platform of today, but it’s already thinking about the future. It acquired Oculus VR for $2 billion in March. Oculus’ virtual reality gaming headset, Oculus Rift, provides an immersive, three-dimensional experience “like [being] on the top of a roller coaster,” says Mendelsohn. She says the device can be used to watch sports like, say, the World Cup. But she’s also thinking bigger. “Imagine taking it further and imagine how we might be teaching a room of children,” continuing Facebook’s mission to connect the world virtually–while also opening up new revenue streams. What this means for advertising pros like Mendelsohn remains unclear, but she’s excited about the acquisition. “If you try [Oculus Rift], you go, “I feel the future.”