Interactions between epithelial and mesenchymal tissues constitute a central mechanism regulating the development of most embryonic organs. Studies on the nature of such interactions require the separation of the interacting tissues from each other and the follow-up of their advancing development in various types of recombined explants. The tissues can be either transplanted and their development followed in vivo, or they can be cultured as explants in vitro. Although the transplantation methods offer certain advantages, including physiological environment and the possibility for long-term follow-up, organ culture techniques are superior in many other aspects. The cultured tissues can be manipulated in multiple ways, and their development can be continuously monitored. The culture conditions are reproducible, and the composition of the medium is known exactly and it can be modified. Furthermore, the in vitro culture conditions allow analyses of the nature of the inductive signals.