National Institute for Medical Research, The Ridgeway, Mill Hill, London, United Kingdom. JP.Vincent@nimr.ac.uk
In the 1960's, Garcia Bellido and colleagues uncovered the existence of developmental compartments in Drosophila. This observation has had a lasting impact on our understanding of developmental mechanisms in flies and vertebrates. Here, I review the work that demonstrated the existence of compartments. I then conjecture on why compartments exist and review the roles of various gene products in the maintenance of compartment boundaries.