The cascade of developmental events in cephalogenesis is initiated by specific genes being transcribed and translated into polypeptides and proteins that form the structural basis of cells and tissues. These become differentiated into the complex organs of the craniofacies by the actions of signalling transducers, growth factors, and morphogens. Defects of development may be traced back through this sequence to determine the specific etiologic factors responsible for dysmorphogenesis. Molecular biology and embryology are becoming increasingly significant for clinicians.