X-Ray CT provides noninvasive means to quantitatively describe 3-D surface crack networks in swelling porous materials, which is used for relating complex and changing geometry to flow and transport processes. Initiation of crack formation and extension of crack networks in soils is primarily related to clay content, clay mineralogy, solute type and concentration, as well as to drying rate. We will present results of well-controlled experiments showing the impact of these factors on development and evolution of crack networks, and discuss advanced qualitative and quantitative analysis of two- and three-dimensional images and structures obtained with X-Ray CT.