Neurometabolic diseases are largely hereditary ones. They encompass lysosomal, peroxisomal, mitochondrial, and polyglucosan diseases as well as amino and organic acidemias/acidurias. Neuropathologically, the entire brain may be affected, i.e. pan-encephalopathy, the grey matter, preferentially being called polioencephalopathy or, when lesions might predominate in white matter, leukoencephalopathies/leukodystrophies. An important issue are extracerebral biopsies that facilitate or allow in vivo diagnosis and may be achieved by electron microscopy. Modern neuropathological techniques may retroactively be applied to archival tissues and those of modern mouse models.