So in this lecture, we're going to focus primarily on the embryonic development of the human embryo. And to see what we mean by these four extra embryonic membranes. Let's take a look at the following diagram. So this diagram describes the developing fetus as well as the four extra embryonic membranes as they sit inside the endometrium of the uterus of that female individual, the mother. Now, the actual developing embryo is this structure here. And notice that the coroner is the extra embryonic membrane, is this structure that encloses not only the embryo but also the other three extra embryonic membranes.