The research is focused on designing interactive products, in particular on the process that leads to the conception of innovative interfaces. The interfaces discussed are tangible interfaces, which exploit their physicality and their material characteristics as input and output mechanisms in the human-product interaction process. The objective of the research is to investigate the use of interaction design methodologies in the design of Smart Material Interfaces: interactive tangible products consisting primarily of smart materials. The overlapping between the discipline of interaction design and the world of smart materials generates new design opportunities. Thanks to this overlapping, objects of daily use become able to convey information through their physical properties and use the material they are made as a communicative medium. The paper is divided in three parts. The first part investigates the role of materials in interaction design, the second part presents the brief of the research and the third one reports an experimental workshop conducted in order to elaborate new interactive metaphors for lighting design.