In the late 1960s, Professor M. Gazi Yaşargil began to systematically incorporate microsurgery into neurosurgical practice, grounded in anatomical expertise and intensive, systematic laboratory training followed by clinical application. Using the operative microscope, he introduced microsurgical techniques and redefined surgical anatomy that had long existed but remained largely unseen. By exploiting natural cisternal pathways to achieve pure lesionectomy, he reintroduced operability for complex pathologies and established new standards in modern neurosurgery. Yaşargil's early contributions to microvascular training and neurosurgical practice exemplify enduring principles from which neurosurgical professionals at all stages can continue to draw guidance. Our exposure to his work—through lectures, publications, and personal communications—profoundly shaped our own approach to neurosurgery and ultimately informed the philosophy underlying our global neurosurgery efforts, embodied in the Madison Microneurosurgery Initiative. This manuscript reviews the historical foundations of microneurosurgery through Yaşargil's early career, his formative laboratory work in Burlington, Vermont, and the systematic clinical implementation of microsurgery in Zurich, distilling key lessons derived from these pioneering experiences. A companion manuscript (Part II) describes how these principles were translated into structured curricula and implemented through contemporary microsurgical training and our global neurosurgery efforts.