The Brain Development period from 1959 to 1972 solidified a migration-and-laminar-organization paradigm for cortical ontogeny. Researchers emphasized radial and multiple migratory pathways as the engines of cortical layering, showing how cells originate near the ventricular surface and populate distinct cortical strata. The period also highlighted region-specific timing of myelin deposition, linking regional maturation to functional emergence and to developmental windows. In addition, the era incorporated cross-species observations and early postnatal dynamics, using Golgi staining, electron microscopy, and thymidine labeling to trace cell movements, synaptogenesis, and proliferative activity. Collectively, these studies structured a cohesive view of development as a temporally sequenced, migration-driven process that establishes the scaffold for later circuitry and specialization.