Having been deaf since birth, three-year-old Grayson Clamp was the first child in the US to receive an experimental cochlear implant - a microchip implanted at the base of his brain.
Watch the moment when doctors switch on the implant for the first time... and the first voice he hears is his Daddy's.
https://www.youtube.com/watch?v=-GA9gEh1fLs&feature=youtu.be
