All the surface of the human body is represented in the cerebral cortex in a transversal band localized at the external part of the cerebral hemispheres: the somatosensory cortex. Each body region occupies in that band a distinct extension depending on its use and sensitivity. For instance, the hands and the lips, on which humans rely most, occupy the largest area. Thus, the 3D representation of that map forms the known sensory homunculus.