An oligodendrocyte (perineuronal) is seen towards the top of the image. The large cell with the processes is a neuron. Note its pale nucleus and prominent nucleolus. The little cell (mostly the nucleus) pressed up against it is an oligodendrocyte. Of course, oligos also send out processes which surround fibers. Note the myelinated fibers in the neuropil. Brain stem - paraphenylene diamine stain, mouse. Plastic-embedded, 0.5 μm section.