The activity of speculating through artefacts (from the more material and tangible to the more immaterial and intangible), produces fictional worlds and opens up possibilities. Prototyping is a way to explore the borders of the possible, ques-tioning different forms of materialization that are not meant to reproduce or reshape products but to explore scenarios embedded in materials, actions, performance, and possible futures. The aim of a prototype is not to predict the future but engaging with possible future solutions addressing the preferable one with a critical perspective. As authors of this chapter, we selected two cases in which prototypes are considered tools for dialogue and reasoning along the development process. For the first ca...