Shared spaces for remote collaboration are nowadays possible by considering a variety of users, devices, immersion systems, interaction capabilities, navigation paradigms, etc. There is a substantial amount of research done in this line, proposing different solutions. However, still a more general solution that considers the heterogeneity of the involved actors/items is lacking. In this paper, we present MIME, a mixed-space tri-collaborative system. Differently from other mixed-space systems, MIME considers three different types of users (in different locations) according to the level of immersion in the system, who can interact simultaneously – what we call a tri-collaboration. For the three types, we provide a solution to navigate, point at objects/locations and make annotations, while users are able to see a virtual representation of the rest of users. Additionally, the total number of users that can simultaneously interact with the system is only restricted by the available hardware, i.e., various users of the same type can be simultaneously connected to the system. We have conducted a preliminary study at the laboratory level, showing that MIME is a promising tool that can be used in many real cases for different purposes.Shared spaces for remote collaboration are nowadays possible by considering a variety of users, devices, immersion systems, interaction capabilities, navigation paradigms, etc. There is a substantial amount of research done in this line, proposing different solutions. However, still a more general solution that considers the heterogeneity of the involved actors/items is lacking. In this paper, we present MIME, a mixed-space tri-collaborative system. Differently from other mixed-space systems, MIME considers three different types of users (in different locations) according to the level of immersion in the system, who can interact simultaneously – what we call a tri-collaboration. For the three types, we provide a solution to navigate, point at objects/locations and make annotations, while users are able to see a virtual representation of the rest of users. Additionally, the total number of users that can simultaneously interact with the system is only restricted by the available hardware, i.e., various users of the same type can be simultaneously connected to the system. We have conducted a preliminary study at the laboratory level, showing that MIME is a promising tool that can be used in many real cases for different purposes.