Neurons are polarized cells in which multiple dendrites and a single axon are formed. Because neurons receive information via dendrites and transmit the information by the axon, the neuronal polarization is an essential process to generate functional neural networks. Interestingly, the polarization can even happen in a single cultured neuron. In this lecture, we will discuss how neuronal polarity is established. You are welcome to imagine possible mechanisms to explain the neuronal polarization.