Digital Twins (DTs) are an established means in machine and civil engineering, healthcare, and agriculture for planning, life cycle management, modeling and simulation, process optimization, as well as for predictive analysis. An emerging application of DTs is metaverse-like applications where people from all over the world can share parts of their physical environment and interact in a virtual space, blending the individual environments together. In this chapter, we examine the challenges in the construction, processing, sharing, and updating of DTs for physical environments and humans and present recent research results. We also discuss potential synergies between emerging Sixth Generation (6G) technology and DTs where, on the one hand, new radar-based sensing features can help improve and update DT, and, on the other hand, DTs can be used to incorporate network quality features into path planning approaches. Furthermore, we analyze applications that bring together groups of people remotely in hybrid mixed reality applications. Finally, we inspect the important scenario of a surgery room and discuss challenges and opportunities for the use of DT and 6G technology.