The cerebrum cortex is composed of six layers: the outermost is the molecular layer, which contains numerous fibres and only a few neuronal cell bodies. - Beneath this is the external granular layer, containing interneurons called granule cells, and glial cells. - The next layer, which is the thickest layer, is the external pyramidal cell layer, composed of pyramidal cells, granule cells and neuroglia. - Beneath this are three more layers of grey matter (internal granular, internal pyramidal, and multiform layer) and white matter (dendrites).