Mapping the brain's fiber network is crucial for understanding its function and malfunction, but resolving nerve trajectories over large fields of view is challenging. Electron microscopy only studies small brain volumes, diffusion magnetic resonance imaging (dMRI) has limited spatial resolution, and polarization microscopy provides unidirectional orientations in birefringence-preserving tissues. Scattered light imaging (SLI) has previously enabled micron-resolution mapping of multi-directional fibers in unstained brain cryo-sections. Here, we show that using a highly sensitive setup, computational SLI (ComSLI) can map fiber networks in histology independent of sample preparation, also in formalin-fixed paraffin-embedded (FFPE) tissues including whole human brain sections. We showcase this method in new and archived, animal and human brain sections, for different stains and steps of sample preparation (in paraffin, deparaffinized, stained) and for unstained fresh-frozen samples. Employing novel analyses, we convert microscopic orientations to microstructure-informed fiber orientation distributions (μFODs). Adapting MR tractography tools, we trace axonal trajectories via orientation distribution functions and microstructure-derived tractograms revealing white and gray matter connectivity. These allow us to identify altered microstructure in multiple sclerosis and leukoencephalopathy, reveal deficient tracts in hippocampal sclerosis and Alzheimer's disease, and show key advantages over dMRI, polarization microscopy, and structure tensor analysis. Finally, we map fibers in non-brain tissues, including muscle, bone, and blood vessels, unveiling the tissue's function. Our cost-effective, versatile approach enables micron-resolution studies of intricate fiber networks across tissues, species, diseases, and sample preparations, offering new dimensions to neuroscientific and biomedical research.