Brain development results from the realization of successive genetic programs at different ontogenic stages. The main stages of brain development include the production of neurons, their migration, the programmed death of a significant proportion of neurons, the production of axons and dendrites, the elimination of excess neurites, synaptogenesis, elimination and selective stabilization of synapses where microglia play a central role, the production of astrocytes and oligodendrocytes, myelination, and angiogenesis. These different stages of brain development and maturation are controlled by intrinsic factors (genetically determined) and modulated by extrinsic environmental factors. This modulation by environmental factors can bring into play epigenetic mechanisms.