So we have three different types of cells. We have these light purple cells that make up the ectoderm layer, the innermost layer. We have these red mesodermal cells that make up the middle mesoderm layer. And then we have the innermost cells, these brown cells that make up the endoderm germ layer. And each one of these germ layers gives rise to many different types of structures and organs. So let's begin by focusing on the ectoderm.