Imagine a world in which your laptop or mobile device accesses the internet, not via radio waves – or WiFi – as it does today but by using light instead: LiFi. Well, that world may not be as far away as you might think. In fact, the technology is already here; and it’s thanks in large part to the engineering ingenuity of Harald Haas, Distinguished Professor of Mobile Communications and Director of the Li-Fi Research and Development Centre at the University of Strathclyde. He tells Jim Al-Khalili about the two decades he has spent researching optical wireless communications, building up to his LiFi breakthrough in 2011, where he made waves in the scientific community and beyond by showing how a simple desk lamp could be used to stream a video. Harald’s research could well have a very real impact on people’s lives, reinventing the way we connect online – but, as Jim hears, his early life was dogged by a very real fear he may have the same devastating disease that took his mother's life at an early age; an experience that shaped his early years and which has driven him to succeed in his own life and career. Produced by Gerry Holt.