A neuron propagates electrical signals and allows communication to take place between different types of cells. And we have many examples of these specialized cells. Now that's pretty fascinating because if we go way back to the beginning of embryological development when we first form that zygote, the zygote is actually only a single cell and it is not specialized in any way whatsoever. Yet that zygote somehow knows to divide and somehow knows to form the different types of cells that exist within our adult human body. So the question we're going to address in this lecture is how exactly does an unspecialized cell know to begin a certain set of processes that eventually allows it to form a special type of cell? So how does an unspecialized cell know, for example, to form a muscle cell and not a nerve cell?