Abstract: The central nervous system (CNS) is characterized by a remarkably elaborate cellular architecture comprising large numbers of glial and neuronal cells with enormous functional diversity, organized into highly complex and specific networks. During development, the various neural cell types must first be correctly specified, then assume their appropriate positions through carefully choreographed cellular migration, and finally establish and refine their functional connections, often over long distances. The end result of all these processes is an extraordinarily intricate anatomical structure, able to receive, integrate, and store information and orchestrate appropriate responses.