This study presents a noninvasive method for tracking neuronal fiber pathways in the living human brain using diffusion tensor magnetic resonance imaging (DT-MRI). The technique leverages the unique ability of MRI to characterize water diffusion, enabling the reconstruction of fiber trajectories throughout the brain by tracking the direction of fastest diffusion. This approach allows for the identification of anatomical and functional connections between brain regions, providing insights into the organization of the human nervous system. The method involves tracking diffusion directions from a grid of seed points and selecting tracks that connect anatomically or functionally defined regions. The study demonstrates the ability to track fiber bundles in various white matter classes, including the corpus callosum, geniculo-calcarine tract, and subcortical association pathways. The results show that tracks can navigate through complex structures, revealing topologies consistent with animal tracer studies and retinotopy in humans. The approach enhances modern imaging by enabling the study of fiber connections among anatomically and functionally defined brain regions in individual human subjects. It provides a means to compare structural differences in brain organization between normal and abnormal states and to study potential fiber connections between functional brain regions. The study also highlights the limitations of current fiber tracking methods, including the difficulty of tracking into cortical gray matter due to low anisotropy and the potential impact of spatial resolution on tracking small and complexly arranged fiber bundles. Despite these limitations, the method offers a powerful tool for understanding the organization of the human brain, combining functional and connectional assessments in individual subjects. This approach has the potential to advance our understanding of brain systems in both normal and abnormal conditions.This study presents a noninvasive method for tracking neuronal fiber pathways in the living human brain using diffusion tensor magnetic resonance imaging (DT-MRI). The technique leverages the unique ability of MRI to characterize water diffusion, enabling the reconstruction of fiber trajectories throughout the brain by tracking the direction of fastest diffusion. This approach allows for the identification of anatomical and functional connections between brain regions, providing insights into the organization of the human nervous system. The method involves tracking diffusion directions from a grid of seed points and selecting tracks that connect anatomically or functionally defined regions. The study demonstrates the ability to track fiber bundles in various white matter classes, including the corpus callosum, geniculo-calcarine tract, and subcortical association pathways. The results show that tracks can navigate through complex structures, revealing topologies consistent with animal tracer studies and retinotopy in humans. The approach enhances modern imaging by enabling the study of fiber connections among anatomically and functionally defined brain regions in individual human subjects. It provides a means to compare structural differences in brain organization between normal and abnormal states and to study potential fiber connections between functional brain regions. The study also highlights the limitations of current fiber tracking methods, including the difficulty of tracking into cortical gray matter due to low anisotropy and the potential impact of spatial resolution on tracking small and complexly arranged fiber bundles. Despite these limitations, the method offers a powerful tool for understanding the organization of the human brain, combining functional and connectional assessments in individual subjects. This approach has the potential to advance our understanding of brain systems in both normal and abnormal conditions.