Much of our present understanding of the pathogenesis in multiple sclerosis (MS) and other disorders of the central nervous system (CNS) is based on information gained through studying experimental animal models. Whereas the investigation of human tissue samples—obtained by biopsies or postmortem—can provide only a focused view at one given time-point in the disease process of which the precise pathobiological history cannot be ascertained, such animal models offer an excellent tool to study the pathogenesis and evolution of the entire course of the disease.