1. Ectoderm: This is the outermost layer. It develops into the outer layer of skin, the nervous system, and sensory organs.

2. Mesoderm: This is the middle layer. It develops into muscles, bones, circulatory system, and reproductive organs.

3. Endoderm: This is the innermost layer. It develops into the lining of the digestive system, respiratory system, and some glands.

These layers are established during the embryonic development of most animals, and they are crucial for the formation of different organs and tissues.