 In this paper, the authors present a new methodology for studying the water retention curve, WRC. They use AXRAY computed tomography, CT, to observe the changes in the microstructure of a sand sample during cyclic drainage and imbubition. This allows them to measure and study the capillary state variables, which are related to the macroscopic WRC. The authors believe their findings will provide valuable insight into the microstructural origins of water retention behavior, including its hydraulic hysteresis and clues for effective stress in unsaturated granular soils. This article was authored by Marius Milatz, Edward Ando, Joachino Vigiani, and others.