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, is coloured red/orange. The light orange curved region in centre is the corpus callosum, a broad band of nervous tissue that connects the two cerebral hemispheres. The isolated structure beneath the rear of the cerebral hemispheres is the cerebellum. Immediately to its left is the brainstem, an enlarged extension of the spinal cord.