The National Eye Institute of the US National Institutes of Health (NIH) has launched a competition to develop a working model of the human retina from stem cells — namely, the 3-D Retina Organoid Challenge (see www.nei.nih.gov/3droc). This will help to clarify the mechanisms of retinal disease, stimulate new technologies and develop more effective therapies (see also G. Quadrato et al. Nature 545, 48–53; 2017).

There are other promising examples of NIH-funded 3D human-tissue models. Tissue chips are being derived from induced pluripotent stem cells in the Microphysiological Systems Program at the National Center for Advancing Translational Sciences in Bethesda, Maryland. And 3D biomimetic systems are being developed in the National Cancer Institute's Cancer Tissue Engineering Collaborative Research Program.

The 3D Retina Organoid Challenge will run alongside the National Eye Institute's Audacious Goals Initiative, which aims to restore vision by regenerating retinal neurons and their connections to the brain (www.nei.nih.gov/audacious).