Jensflorian [creativecommons license] via Wikimedia CommonsPrion diseases are unusual, infectious, potentially deadly, neurodegenerative diseases caused by transmission and toxic accumulation of misshapen prion protein (PrP) in the brain. A lack of animal models that accurately recapitulate prion disease pathology has impeded our understanding in this area; therefore, the characterization of new mouse models of fatal familial insomnia (FFI) and Creutzfeld-Jakob disease (CJD), two prion diseases that are fatal in humans, represents a welcome advance.