Sagittal section of a human brain. It has been coloured to show the location of the pineal gland (red) and its neighbouring structures: corpus callosum (yellow), cavum septum pellucidum (purple), fornix (light green), tela choroidea (green), third ventricle (light brown), mammillary body (pink), midbrain tectum and tegmentum (blue), cerebral aqueduct (light blue) and cerebellum (light purple).