Far from using the term transmedia as a simple adjective to characterise certain nouns, nowadays, transmediality can be considered a real way to execute projects tackling the complexity of the contemporary media scene. The aim of this work is to define the Transmedia Design discipline, by describing the project and research activities carried out at Politecnico di Milano, placing special emphasis on the Plug Social TV project. The main aim of the project is to test drive the communication processes and instruments which, through building storytelling worlds and their strategic and multichannel distribution (analogue and digital), can support the creation of a dialogue between interested parties present in the territory.