(Vox) – A medical field that almost died is quietly fixing one disease at a time.

In a lab room, a toddler, deaf from birth, sits while a tone plays. There’s no reaction. His face does not change.

Six weeks later, after a single injection of an experimental gene therapy, the same toddler is back in the same room. The tone plays. The toddler’s head turns toward the sound. And somewhere just off screen, the child’s grandfather says his name. The boy turns and looks. He can hear. (Read More)