<P> The unusual surface appearance of the cerebellum conceals the fact that the bulk of the structure is made up of a very tightly folded layer of gray matter, the cerebellar cortex . It has been estimated that if the human cerebellar cortex could be completely unfolded it would give rise to a layer of neural tissue about 1 meter long and 10 centimeters wide--a total surface area of 500 - 1000 square cm, all packed within a volume of 100 - 150 cubic cm . Underneath the gray matter of the cortex lies white matter, made up largely of myelinated nerve fibers running to and from the cortex . Embedded within the white matter--which is sometimes called the arbor vitae (Tree of Life) in the cerebellum because of its branched, tree - like appearance--are four deep cerebellar nuclei . </P> <P> The cerebellum can be divided according to three different criteria: gross anatomical, phylogenetical, and functional . </P> <P> On gross inspection, three lobes can be distinguished in the cerebellum: the flocculonodular lobe, the anterior lobe (rostral to the "primary fissure"), and the posterior lobe (dorsal to the "primary fissure"). The latter two can be further divided in a midline cerebellar vermis and lateral cerebellar hemispheres . </P> <Table> <Tr> <Td> Figure 3: Cerebellum and surrounding regions; sagittal view of one hemisphere . A: Midbrain . B: Pons. C: Medulla. D: Spinal cord . E: Fourth ventricle . F: Arbor vitae . G: Tonsil . H: Anterior lobe . I: Posterior lobe . </Td> <Td> Figure 4: Schematic representation of the major anatomical subdivisions of the cerebellum . Superior view of an "unrolled" cerebellum, placing the vermis in one plane . </Td> </Tr> </Table>

What are the three major regions of the cerebellum
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