Neurons are created through a process called neurogenesis which mostly occurs during the prenatal development of the nervous system when the growing brain is populated. Key times of embryonic neural development include the birth and differentiation of neurons from stem cell precursors, the migration of immature neurons from their birthplaces in the embryo to their final positions, outgrowth of axons from neurons and guidance of the motile growth cone through the embryo towards postsynaptic partners, the generation of synapses between these axons and their postsynaptic partners, the neuron pruning that occurs in adolescence, and finally the lifelong changes in synapses which are thought to underlie learning and memory.
