As with any other organ, the brain can also be a target for particles. The blood-brain barrier, an anatomical and functional unit made up of endothelial cells of the vessels that supply the central nervous system and protect it from various types of aggression, has no effect on the particles that, therefore, reach the brain where they cause forms of cancers such as the astrocytoma that can result in glioblastoma. Even the cerebro-spinal liquor, a liquid which, among its various functions, has that of enveloping the central nervous system, lightening its weight and cushioning possible impacts, may contain particles of external origin. Our research on the brains of suddenly-died babies (SIDS) and those of cows affected by mad-cow disease has shown the presence of massive quantities of particles.