José Antonio Campos-Ortega (1940-2004), a Spanish scientist who became a leading figure in the developmental genetics of the nervous system, spent most of his scientific life in Germany. Nevertheless, he remained deeply rooted in his native country. His thinking, his ambition and his work were driven by scientific, philosophical and historical questions. He started as a neuroanatomist, working first in Valencia, then in Göttingen, Tübingen and Freiburg. He used primates, reptiles, then the house fly and finally Drosophila to address the question “How is the brain or the eye structured in order to function?”. While in Freiburg, the problem shifted to “How does the nervous system come into being, into form?” Campos-Ortega tried to understand early neurogenesis in Drosophila through formal genetics, by identifying relevant genes and studying their genetic interactions. Since he was convinced that not only a single experimental approach could solve a problem as complex as the development of the nervous system, he also included the molecular biological approach when he moved to Cologne, while maintaining a strong focus on anatomy, embryology and genetics. There, he also started to work on the neurogenesis of the zebrafish, using similar concepts and approaches. Throughout his scientific career, he thought, wrote and taught about the evolution of methods and ideas in his field of research. At Campos-Ortega’s early death, an unfinished book manuscript was left, entitled “Developmental Genetics. The Path to the Biological Synthesis”. Some parts of his introductory overview are included here.