Each neuron begins life as a progenitor cell. These cells form in the central part of the developing brain and then move outward along the supportive glial cells until they reach their pre-programmed location in the brain. As a progenitor cell reaches its destination its status changes and it now is "committed" to become one of numerous types of neurons. The neuron begins to grow axons and dendrites. These fibers will eventually form a synapse or connection with those of other neurons. Once the neuron has taken on its specialized function it is considered "differentiated."