Water-cooler chat used to be dominated by last night's TV, but now people are discussing pop science and the latest Brian Cox viral. Over 450,000 people tune into TED Talks every day, while homemade science videos have millions of views. So how has YouTube made science sexy?

British beauty vlogger Zoella already boasts an empire of 6.6 million YouTube followers and a line of branded products. And with her (ghostwritten) novel Girl Online becoming the UK's fastest selling book of 2014, where next?

PewDiePie is the most subscribed channel on YouTube, and its creator makes more than £2 million a year on ad sales. He's one of YouTube's elite – a new generation of hyper-influential media moguls. But why are 30 million teens watching a stranger play video games?

Gen Z had eluded Subway. Teens are watching less live TV, so they don’t see its ads, and they don't like direct advertising. So Subway launched sitcom The 4 to 9ers, and the first season attracted 18 million viewers. But who wants to watch a TV show created by a fast food chain?