Epithelial appendages are the derivatives of the epithelial sheet. On the body surface, they include hair, feathers, scales, claws, horns, sebaceous glands, mammary glands, etc. In the oral cavity, they include teeth, salivary glands, etc. Inside the body, the surfaces of the gut are covered with different derivatives that line the stomach, small intestine, colon, etc. Lung, pancreas and liver begin as epithelial derivatives of the endodermal tube. These organs are diverse in structure and function. However, is there a common theme underlying their formation?This book identifies simple principles underlying the seemingly diverse phenomena of organ formation. Data accumulated so far suggest that most of the molecular mechanisms are shared in different organogenetic processes, in body axis construction, and even have their roots in Drosophila morphogenesis. The new unifying concept is a pleasure to appreciate. Each chapter provides the most up-to date information written by leaders in the field.