(A) Complex tissue microstructure in an MRI voxel of the rat hippocampus, as visualized by 3D electron microscopy. Cellular structures in the tissue hinder the diffusion of water molecules. (B) Advanced diffusion MRI can probe the microstructural information contained within a voxel by detecting the diffusion of water molecules. As epilepsy develops after a brain injury (left to right), the properties of the brain tissue in the hippocampus change, altering the diffusion of the water molecules. The colors in the maps represent the orientation of diffusion (blue represents up-down orientation, red is left-right, and green front-back). (C) The diffusion MRI data can be used to visualize cellular level changes – including cell death, mossy fiber sprouting, the activation of glial cells, and axonal plasticity – that occur as epilepsy develops after different brain injuries. These changes can be visualized by staining the tissue and studying it under a microscope. In the future, this information could help to predict whether epilepsy will develop after a brain injury.