Book excerpt: "Over the past twenty years craniofacial biology has been revolutionized by major developments in our understanding of the cellular, molecular and genetic mechanisms underlying embryonic development. Many of these advances have been based on animal models, most notably the fruitfly Drosophila, the chick and the mouse. Since these developmental processes have been highly conserved during evolution, this information is relevant not only to understanding normal human development but also to understanding how genetic mutations produce particular malformations or inherited diseases. This book incorporates these discoveries into traditional morphological description of craniofacial development, and in a form accessible to clinicians with an interest in the head and neck." --book cover.