A competition for radical ideas in the fight against blindness will move on to its next phase by challenging participants to build prototypes of working human retinas. The National Eye Institute (NEI) 3-D Retina Organoid Challenge (NEI 3-D ROC 2020) is a $1 million federal competition designed to create lab-grown human retinas from stem cells. The organoids developed for the competition will mimic the structure, organization and function of the human retina, the light-sensitive tissue at the back of the eye.