Volume 3 of Advances in Developmental Biology and Biochemistry consists of five chapters that review specific aspects of mammalian, fly, and ascidian development. In Chapter 1, J. Campos-Ortega discusses mechanisms of neurogenesis in Drosophila, with special attention given to the process of separation of epidermal and neural progenitor cells. In Chapter 2, D. Rappolee and Z. Werb discuss the role of growth factors in early mammalian embryos and compare genes used in mouse with those used in Xenopus and chick. In Chapter 3, E. Linney and A.-S. LaMantia discuss the range of malformations resulting from retinoid teratogenesis, the molecular biology of retinoids, the use of transgenic mice to study retinoid signaling, and differentiation of the CNS in the context of retinoid signaling. In Chapter 4, E. Gavis and R. Lehmann discuss pathways and components involved in RNA localization and targeting in Drosophila oocytes. In Chapter 5, W. Jeffery discusses the use of actin as a tissue-specific marker in studies of ascidian development and evolution.