These lipurpose cells shown in this diagram. Now, we also actually form different types of structures that are found inside that developing embryo. The question is, how does that happen? How do cells that are initially on the outer portion of that developing embryo eventually form structures found on the inside of that embryo, on the inside of that fetus? Well, as it turns out, this process of embryological development is actually a complicated process and we not only have cell differentiation and cell growth and cell proliferation but all these cells also move around many times and rearrange themselves inside that developing embryo. In fact, as we discussed in the process of neuralization when we produce the nervous system it's the ectodermal cells that eventually invaginate and move into that embryo and form the neural crests and the neural tube.