As our eyes scan this page, the cells in our retinas are firing off messages. It takes them a split-second to convert this picture – of similar cells inside the retina of a zebrafish – into electrical signals bound for the brain. A high-powered microscope was used here to zoom in on a cross-section of the fish’s retina, highlighting the contours of different layers of cells. The sensitive photoreceptors (the layer of larger, bulky cells on the left) gather light from the outside world, converting it into an electrical signal that penetrates deeper into the retinal tissue (the layers of cells on the right). Meanwhile, the black-coloured, inky pigment cells absorb any excess light, protecting the photoreceptors from damage. Our eyes, it appears, have their own internal pair of sunglasses.
Written by John Ankers
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences (the new name for the MRC Clinical Sciences Centre) the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.