The processes that govern development, from the zygote through the rapid embryonic stages to the formation of a fully developed organism at birth, remain only partially understood. Advancing this knowledge—the study of morphogenesis within the broader field of developmental biology—has been the lifelong work of Antonio García-Bellido at the Spanish National Research Council (CSIC) in Madrid. His pioneering research in Drosophila melanogaster has shed light on key mechanisms of development, from early imaginal discs, mosaic models to the influential compartment theory, which describes how modular genes define territories that guide tissue growth and organization. His work has highlighted the fundamental importance of spatial orientation in achieving proper organismal structure. This foundational research continues to shape the field, providing essential insights for understanding normal development, as well as the origins of malformations and developmental disorders at multiple biological levels.