The structure of cereals and snack foods during processing is developed according to structural changes at various levels of matter organization. At macroscopic scale, two main consecutive mechanisms rule these changes: (1) the transition from a powder (the flour) to a viscoelastic liquid (the dough, the paste) and (2) the transition from a liquid to a solid, soft or rigid. At mesoscopic scale, these changes can be first captured through state diagrams that represent the material rheological properties as functions of the composition. These diagrams and functions can be enriched with the paths followed by the food product along processing. All together, these representations, called basic knowledge models, can provide scientists and engineers with a comprehensive basis to predict the development of structure and final properties of the food. In this chapter, we will strive to apply basic knowledge models for predicting texture properties to several types of airy cereal and snack foods (bread, biscuits, cakes, and extruded snacks taken as examples). A specific effort is devoted to build a generic approach of structure development that can be applied to the design of cereal foods with targeted sensory and nutritional properties.