Fig. 2. Midfourth week embryo after neural tube invagination. Maxillary, mandibular, and frontocranial processes are beginning growth into intended facial position. (Fries PD, Katowitz JA: Congenital craniofacial anomalies of ophthalmic importance. Surv Ophthalmol 35:87, 1990, with permission from Elsevier Science.)