Olfaction is an important sense for recognition, particularly for young mammals that often are born before the eyes or ears are fully functional. Understanding how olfactory information is delivered to and handled by the central nervous system requires knowing the anatomical organization of the projections from the nose to the olfactory central targets, including olfactory cortex. The central olfactory system is highly organized, with clear layering, distinctive cell types, and well-studied projection areas. One approach to clarify how the system works is to observe how the functional circuits develop. Marsupials, such as the opossum, have a very slow early growth after birth, and so provide a particularly useful model system. This project will use anatomical techniques to trace the development of olfactory connections as they form, and to see how functional manipulations affect the early interactions which specify formation of the olfactory system. Results from this model system will be important to developmental biology and to systems neuroscience as well as to understanding brain organization and sensory processing.