Microstructure with diffusion MRI: what scale we are sensitive to?

Diffusion-weighted MRI is the forerunner of rapidly developed microstructure (?MRI) aimed at in vivo evaluation cellular tissue architecture. This brief review focuses on spatiotemporal scales that are accessible using different diffusion techniques and need to weight measurability against interpretability results. Diffusion phenomena models first classified two-dimensional space (the q-t-plane) measurement with narrow gradient pulses. Three-dimensional parameter Stejskal–Tanner weighting adds more this collection. Modern larger number parameters briefly discussed under overarching idea matching geometry targeted cell species.