Three-year-old Grayson Clamp heard his father's voice for the first time a few weeks ago thanks to a new device known as an "auditory brain stem implant."
The North Carolina toddler is the first U.S. child to receive the implant, and video of him hearing his father say "Daddy loves you," has spread across the internet.
Clamp was born without a cochlear nerve, which connects the auditory portion of the inner ear to the brain. But a cochlear implant, which has been successful for others, did nothing for him.
Grayson's adoptive parents, Len and Nicole, enrolled Grayson in the ongoing FDA trial for the "miracle device."
University of North Carolina doctors implanted the microchip inside the boy's brain, and it helps him process and recognize sounds that travel through tubes to his ear.
"We don't know exactly what it's like for him," said Grayson's mom. "We don't know exactly what he hears. His brain is still trying organize itself to use sound."