The goal of this project is to explore novel methodologies to support interaction between realities. By reality, we mean those defined on the Reality-Virtuality continuum by Milgram and Kishino, in addition to our own reality. Scenarios where users might be immersed in Virtual Reality in the same physical location where other non-immersed users might be present, are becoming increasingly more frequent. This introduces the concept of “cross-reality” interaction: an interaction intent expressed by a user present in one type of 'reality’’ which affects another type of reality. For example, a non-immersed user wishing to interact with an object in a Virtual Environment, or an immersed user wishing to send information to external users present outside. In this project three main challenges affecting this novel interaction paradigm will be explored. Namely: how to visualize virtual environments externally and vice versa, how to design cross-reality user interfaces, and how to support cross-reality collaboration.