But on that day, things sure did seem to be working out. The image Yuancheng first texted to me looked like an orange, glowing jellyfish; its head was at the top, where the eye of the mouse sits, with long tentacles flowing down toward the brain. Two weeks earlier, Yuancheng and our collaborators had squeezed the optic nerve a few millimeters from the back of the eye with a set of tweezers, causing almost all the nerve cell axons, the tentacles, to die back toward the brain. They injected an orange fluorescent dye into the eye that is taken up by living neurons. So when Yuancheng took a
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