Damage induced by desiccation (i.e. drying and cracking) is a ubiquitous issue in waste storage engineering. The fundamental mechanisms of the phenomenon of cracking during drying and the ways to control or avoid it are still elusive. This paper presents the results of an experimental program aiming at clarifying the various phenomena leading to desiccation cracking as well as the parameters which control initiation and propagation of cracks. Starting from an initially saturated clayey soil, results show that cracking onset occurs in saturated conditions close to air entry value and shrinkage limit. Mechanisms of shrinkage and cracking are addressed, and especially the critical role of boundary constraints and induced tensile stresses in desiccation crack onset, until tensile strength is reached. Tensile stress generation is the results of a strain compensation mechanism.