The film introduces into the field of contraction phenomena and explains why desiccation cracks are formed. It describes the main features of desiccation cracks using both modern and fossil examples and demonstrates, via time lapse, how desiccation cracks develop in an experiment. The computer reproduces this process plotting the sequence of the digitized cracks. Graphic animation shows the interaction between tensile strength and tensile stress responsible for the information of the orthogonal crack pattern. Finally, the possible geological meaning of desiccation cracks is discussed.