This image is an artistic rendering of a merged confocal image of white matter components in mouse optic nerve. GFAP+ astrocytes (hollow structures bordered by pink) were co-labeled with anti-NOS3 antibody (white areas inside the hollow structures) in young optic nerves. NOS3 isoform is also abundantly expressed in other glial cells such as oligodendrocytes (yellow bordered by green) and play a crucial role in mediating stroke injury in young and aging white matter. For more information, see the article by Bastian et al. (pages 6247–6266).