Glia were until recently regarded as the glue cells of the nervous system. In this chapter, new and unexpected roles of main glia subtypes are discussed, including learning, memory, fear conditioning, long-term potentiation and some complex neurocognitive functions. Different mechanisms have been involved, at the cellular and systemic levels, at least partially explaining these features and usually involving glia–neuron and glia–glia interactions, and suggesting that human brain evolution required a concomitant specialization of both neural types. In addition, evidence involving glial cells in the origin as cause or effectors of different psychiatric pathologies and/or some of their symptoms is also considered. The neural crest is a subpopulation of cells that delaminate from dorsal regions of the neural tube and contribute to many structures of the body, including all the peripheral nervous system. They were shown to migrate toward the rostral regions of the embryonic brain, and this was found to induce the formation of the forebrain from which the neocortex originates. Interestingly, some studies involved the neural crest in certain types of autism and schizophrenia. Moreover, after traumatic central nervous system injury as well as in the context of demyelinating diseases, Schwann-like cells (one of neural crest derivatives) were found to invade and/or remyelinate some axons, thus playing a role in nervous system regeneration and myelin reconstitution. While after injury some peripheral nerves can contribute with these cells through invasion of peripheral nerve components, some of the Schwann-like cells appearing in the affected areas could originate from progenitors of the central nervous system. Finally, the growing spectrum of Schwann cell progenitor derivatives is also herein discussed, with evidence suggesting a developmental plasticity and differentiation potential much broader than expected in neural committed cells.