This lecture outlines a research approach, procedure and strategy aimed at the development of clay modeling in the context of natural clays of varying geological history. The aim is at providing evidence of the clay features causing given behavioral facets, at the micro to the meso-scale, in order to connect classes of behavior and corresponding models, to classes of clays. The approach to micro-macro is not that of deducing macro-behavior from modeling the micro-processes, not so feasible for clays, but to join systematically the knowledge of the micro to meso features and processes and the observations of macro-response. The procedure entails the development of analyses spanning from those generally carried out in clay science, at the micro-scale, to characterizations of the meso-scale, to analysis through element testing of the macro-behavior. Furthermore, the procedure includes studies of the geological history of the material. Examples of application of the research strategy to different case studies are presented, that document how it is possible to both identify the internal factors generating given clay behavioral facets and model clay behavior within a simple general framework. This framework represents an example of formalization of the variability of clay response with the micro to meso-features of the clay.