Many events that shape the developing animal embryos involve rearrangements of simple epithelial sheets into more complex three-dimensional structures, a process termed epithelial morphogenesis. Epithelial organ development is achieved through inductive interactions between different tissue types, typically between epithelial and mesenchymal tissues. Although the signaling pathways regulating epithelial-mesenchymal crosstalk have been largely identified, our understanding on how these signaling activities are translated into coordinated changes in cell behavior: proliferation, apoptosis, migration, or adhesion, is still rudimentary. Dissecting the details of organogenesis will be important for understanding the causes and developing cures when things go wrong as seen in developmental disorders or in tumorigenesis, as well as for advancing methods for organ regeneration.