First step in wiring the nervous system together is the generation of neurons. Later in development, horizontal cleavage is the rule. Cell migration: many daughter cells migrate by slithering along thin fibers that radiate from the ventricular zone toward the pia, these fibers are derived from specialized radial glial cells, providing the scaffold on which the cortex is built. In this way, the cortex is said to be assembled inside-out. Cells destined to become neocortical pyramidal cells will often assume the same culture characteristic dendritic architecture in tissue culture. Differentiation of cortical areas: most cortical neurons are born in the ventricular zone and then migrate along radial glia to take up their final position in one of the cortical layers. Slit is an example of a chemorepellent: chemorepellent- a diffusible molecule that chases axons away. For slit to exert this action, the axon must express on its surface the slit receptor, a protein called robo.