This confocal image shows a retina prepared from a GLT1-EGFP mouse. The widely used astrocyte marker GLT1 (green) is highly expressed by neurons in the outer nuclear layer, while SOX9 (purple) is most prominent on Müller glial cells, as identified by glutamine synthetase (white). Cell nuclei are labeled by DAPI (blue). For more information, see the article by Sun et al. (pages 4493–4507).