In biological science, we can only see parts of the head and the cells contained in them. it's all easy to learn, because there is special material about it (brain).
However, it is difficult for us to determine the shape of the brain, because every human being is not the same shape and size. the size of a person's head is determined by the shape of the body that will balance the head, as well as the part of the contents contained in it.
@aranna