Mouse Cone Cells (IMAGE) Cell Press Caption This image shows cone photoreceptors (green) in a slice from a mouse retina. A majority of the photoreceptors (97%) in the retina are rods (black). The black layer on top of the photoreceptors is retinal pigment epithelium. Credit Jung-Woong Kim Usage Restrictions Credit Required. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.