As a laboratory of developmental biology, our guiding interest is to comprehend how complex biological patterns can be assembled with stereotyped precision. This requires a detailed understanding of how cells come to execute appropriate behaviors — be it adoption of specific cell fates, proliferation, or apoptosis — and do so at the right times, in the right places, and in the right numbers. Dysfunction of processes that direct normal tissue patterning results not only in developmental disorder but also underlies adult disease. Tellingly, many factors whose mutation is relevant to human cancer were first identified and characterized with respect to development in model organisms.