Advances in multiscale myelin imaging: from classical histology to functional insights

Scientific understanding of myelin, the lipid-rich sheath of axons essential for vertebrate rapid neuronal communication, has evolved considerably. Enabled by major advances in imaging technology, research has shifted from viewing myelin as a static insulator to investigating the dynamic roles of myelinating glia in nervous system development, function, and pathophysiology. This review aimed to provide a comprehensive, multi-scale overview of the imaging toolkit for myelin biology, from foundational histology to cutting-edge advances. At the macro- and meso-scales, non-invasive modalities like magnetic resonance imaging and positron emission tomography reveal <i>in vivo</i> myelin architecture and molecular changes, offering critical insights into large-scale pathology. At the micro-scale, advanced light microscopy now visualizes cellular dynamics and molecular interactions with remarkable clarity. Finally, at the nano-scale, sophisticated electron microscopy techniques-including volume electron microscopy and correlative approaches-resolve the ultrastructural basis of biological phenomena with unparalleled detail. As no single modality can capture the full biological context, a holistic understanding of glial biology requires the strategic integration of these multi-scale techniques with advanced computational analysis. This integrated approach is essential for revealing the full spectrum of myelin biology and uncovering novel targets for therapeutic intervention.