False-colour nuclear magnetic resonance (NMR) image of a mid-sagittal section through a human head, showing structures of a normal brain, airways & facial tissues. The heavily-folded cerebral cortex (the grey matter), which forms the outer part of the cerebrum, appears green, yellow & red. Beneath it at right appears the feathery outline of the cerebellum. Immediately to the left of the cerebellum in red are the structures of the brainstem, an enlarged extension of the spinal cord. The uppermost bones of the neck are seen to the left of the spinal cord. The airway of the throat & cerebro-spinal fluid surrounding the brain & spinal cord appear dark blue.