Computing systems can function as augmentation of individual humans as well as of human societies. In this contribution, we take mirror worlds as a conceptual blueprint to envision future smart environments in which the physical and the virtual layers are blended into each other. We suggest that pervasive computing technologies can be used to create a coupling between these layers, so that actions or, more generally, events in the physical layer would have an effect in the virtual layer and viceversa. On top of this, wearable technologies and augmented reality techniques enable new forms of user interaction with the smart environment and with other users. Mirror worlds so conceived will enable temporal, individual, and social augmentations. We conclude by elaborating on some possible consequences at the societal level.