And the umbilical vesicle eventually becomes part of the umbilical cord system. And we also form this cavity that is created by the epiblast cells. And this is known as the amniotic cavity. And this is where that organism of the fetus will actually be found, as we'll see in just a moment. Now, we also have this extension of the Trophy Blast, this purple section that will develop into the coriane and ultimately into the placenta. Now, when we go from diagram three to diagram four, something important takes place.