What if the standard anatomical maps of the brain have been wrong for over a century, and the molecular evidence was there all along? Neuroanatomist Luis Puelles from the University of Murcia explains how developmental biology and gene expression mapping overturned the dominant columnar model of brain organization, revealing a segmental architecture that had been proposed and forgotten decades earlier. Subscribe for more from the Convergent Science Network podcast series. Luis Puelles, one of the leading figures in developmental neuroanatomy, joins Paul Verschure and Tony Prescott at the Convergent Science Network podcast to discuss his career-long effort to replace the columnar model of brain organization with a prosomeric model grounded in embryological evidence. The conversation traces Puelles' intellectual trajectory from an initial interest in how the mind emerges from the brain, through frustration with psychology disconnected from neurobiology, to decades of work on the spatial organization of the developing neural tube. The central argument is that brain boundaries are transversal to the neural tube axis, not longitudinal as the dominant American school proposed since 1910. Puelles describes how he arrived at this conclusion through morphological observation of embryos long before molecular genetics provided confirmation. When gene expression mapping became possible, the data immediately validated his model, showing that genes code for boundaries exactly where his framework predicted them. The conversation explores the historical context of the competing columnar model proposed by Herrick, which extrapolated brainstem nerve component analysis to the entire forebrain without embryological support. Puelles explains why this model persisted for 60 years despite being inconsistent with developmental biology: it offered functional interpretations that appealed to the field, even though those interpretations lacked causal mechanisms. His collaboration with molecular biologist John Rubenstein proved pivotal, combining Puelles' morphological expertise with gene expression data that other embryologists had dismissed as meaningless. The discussion addresses the relationship between structure and function in neuroscience, with Puelles arguing that understanding morphology requires understanding development, and that functional analysis must be consistent with the causal mechanisms operating in the embryo. Part of the Convergent Science Network podcast series from the BCBT Winter School.