Within a brain nerve cell, or neuron, the axon is the long, wiry extension that carries electrical impulses to a neighboring neuron. Just like household wires, these biological versions (shown in orange) need insulation to function properly; without it, central nervous system disorders can develop. A fatty substance called myelin (shown in yellow) serves this important purpose. In this view, magnified 10,000 times, myelin encases the axons of a mouse’s spinal nerve root, part of the spinal cord that communicates with the brain. Thomas Deerinck and Mark Ellisman of the National Center for Microscopy and Imaging Research at University of California, San Diego, took this picture while researching cellular architecture.