Neuronal migration has a key role in the formation of a functional six – layered cerebral cortex. Development of a functional cortex is a highly complicated process involving not only neuronal migration, but also neuronal production (via symmetric and asymmetric cell division) and modification of neuronal circuits (via synaptogenesis and apoptosis). The localization and timing of neuronal proliferation and neuronal migration define the identity, laminar positioning, and specific connectivity of each cortical neuron. Neurons start to migrate from their place of origin – proliferative zones of the developmental telencephalon (ventricular and subventricular zone), until they reach their final destination – the cortical plate. Neurons that originate from the cortical VZ migrate radially to the CP and mainly become glutamatergic projection neurons. In contrast, neurons derived from ganglionic eminences (MGE and LGE) migrate tangentially and give rise to GABAergic interneurons, which are incorporated into local neuronal circuits in the cerebral cortex. Both projection neurons and interneurons are located in 'inside – out' sequences in the cortical plate, that is, the early – born neurons are situated in the deep layers of the cortex, whereas the late – born neurons ultimately reside in the superficial layers. During migration, neurons change shape as well as mode, speed and direction of movement and gene expression. Alterations at any step of this process – due to mutations or environmental factors – lead to defined brain pathologies collectively known as malformations of brain development, which are now recognized as one of the leading causes of drug – resistant epilepsy and intellectual disability. Most common of those are lissencephaly, periventricular heterotopia, focal cortical dysplasia and polymicrogyria. All of them cause severe disabilities and at the same time treatment options are extremely modest.