How does the human eye transform waves of light into the vivid, detailed experience we call vision? In this episode of CortexCast, we follow photons on their journey from the moment they strike the retina to the point where visual signals begin to take shape. We explore the cascade of biochemical reactions triggered by molecules such as retinal and rhodopsin, the roles of rod and cone cells in night and colour vision, and the vulnerability of the central retina in age-related macular degeneration. We then turn to the networks of bipolar and horizontal cells, where visual information is funnelled, filtered, and sharpened into receptive fields — the brain’s earliest building blocks of images. Along the way, we uncover how a patch of neural tissue at the back of the eye becomes the gateway to our entire visual world.