So this is the innermost layer found in that developing organism, in that developing embryo. And this is called the endoderm. Now, the endoderm layer gives rise to the epithelial layer of the lungs, our digestive system, the pancreas, the bladder, the liver, and it also forms the thyroid and the parathyroid gland as well as the thymus. And finally, what about the mesoderm? Well, the mesoderm is the middle layer of the developing embryo. It's found between these two layers.