Ectoderm
Imagine you're redecorating a room, starting with the walls which form the outermost part of the space. Similarly, in the development of most animals, the ectoderm is like the "wallpaper" of the embryo, forming the outer layer called the gastrula. Just as the wallpaper sets the tone for the room's design and is the first thing people notice, the ectoderm develops into the outermost structures of the body, like skin and the nervous system, providing the initial foundation for an organism's external appearance and protection.
Practice Version
Ectoderm: Outer germ layer in most animals, it develops from the outer surface of the gastrula. Ectoderm. Ectoderm is the layer of cells in an embryo that forms structures like the skin and nervous system.