Models generally fall between two extremes: ‘models of the tissue’ and ‘models of the signal’. Models of the tissue6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 describe the underlying tissue microstructure in each voxel explicitly with a multi‐compartment approach.18, 19, 20 Models of the signal focus on describing the DW signal attenuation without describing the underlying tissue composition that gives rise to the signal explicitly.21, 22, 23, 24, 25, 26, 27, 28, 29 Other approaches fall between these two classes and include some features of the tissue, such as the distribution of fibre orientations, but often describe the signal from individual fibres without modelling the fibre composition explicitly.30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40