Within the dull human organism, we have billions upon billions of individual cells. And on top of that, we have over 200 different types of cells that each carry out their own specific function which have their own specific role in our body. For example, one specialized type of cell is a neuron. 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.