Apple technology has revolutionised the world. The US company says there are now more than 1.5 billion Apple devices in active use globally - a billion of those are iPhones. It was 15 years ago this week that the co-founder of Apple, Steve Jobs, first unveiled the iPhone.

So how do you come up with such a world-changing idea? We find out from Tony Fadell - the co-inventor of the iPod and iPhone. He tells Jo Critcher how it took years of set-backs to find success and how it's important to never give up.

Having invented the Nest smart thermostat, Tony explains why he's now focused on green technology. He's tells us how he's investing in tech start-ups with his company, Future Shape, that are helping to find solutions to the climate change crisis.

Presenter and producer: Jo Critcher

(Image; Tony Fadell: Credit; BBC)