This chapter is focused on the analysis of the shell microstructure of different taxa and on how this information can be used for paleoenvironmental interpretations. A physic-chemical analysis on Modern, Holocene and Pleistocene shells of the purple clam Amiantis purpurata helps discern the structural changes during early diagenesis. In addition, the analyses of the microstructure of two other bivalves (Glycymeris longior and Ameghinomya antiqua) from the same region explain the differences in the degree of fragmentation in both species as a result of different structural features. Finally, cathodoluminiscence applied to Tawera gayi provides information on the skeletal growth cycles that is useful for evaluating changes.Facultad de Ciencias Naturales y Museo