Several studies on neurobiology have contributed to our understanding of the genesis, survival and death of neurons, unquestionably the stars of the Central Nervous System (CNS). However, they would not be so famous without their close associates: the glial cells. Since novel studies have demonstrated new and important functions for glial cells, they are beginning to gain significant importance in brain research to allow us to reinterpret long known functions on the basis of new concepts. Here, we review recent progress in our understanding of the role of glial cells in the biology of tissue development and maturation.