The characteristics of perceived "texture" are determined by different physical and physicochemical properties of the food and by the unique and complex features of the human sensory systems. This chapter surveys the mechanical terminology and describes the main rheological methods of solid foods characterization. It focuses on the physical significance of the results in the context of solid foods and their unique structures. The interested reader, however, will be able to find ample material on rheological models and the mathematical aspects of rheological data processing methods in the selected references that are cited in the text and in the general literature of rheology, mechanics, and material science. The fundamental principles of rheological evaluation of foods, however, are basically the same as those that are applicable to engineering materials, especially polymers. There are, however, differences in the interpretation of the test results.