This image shows a repeating pattern of electroretinogram traces from wild-type (white) mouse retinas and retinas in which the hyperpolarization-activated cation channel HCN1 was knocked out selectively in rods (cyan). The traces show a family of responses to a repetitive flash of light at increasing frequencies. The traces are overlain on the pupil of an eye with a blue iris. This reveals that in the absence of HCN1, rod signaling is prolonged and suppresses cone signaling. For more information, see the article by Lankford et al. (pages 4231–4249). Cover image: Sheila Baker with eye image from magic26/shutterstock.com.