Synthetic, digital 3D immersive realities have been known by multiple names, differing slightly: Virtual Reality (VR) Extended Reality (XR) Augmented Reality (AR) and Mixed Reality (MR), The first is a virtual representation of a world, that feel real, yet does not necessarily follow the physical reality as known to us, and might for instance include imaginary objects, imaginary animals with impossible capacities, such as talking animals. It might include 3D images of other humans, that look real, or not, and might include representations of humans that are interactive and represent a human, yet do not look like the represented entity, and rather take the shape of an animal, real or imaginary, as chosen by the user. Augmented reality is physical reality that includes on top of the physical varying features–such as names of people, height or names of buildings, driving instructions on top of a representation of a 3D image of a city, details describing the science and effect on humans of the Vesuvius volcano eruption, more than 2000 years ago, or explanation regarding the various phases of a pumping heart of engine. Extreme reality (XR) goes a step further and might include components that can act on the user such as measures of stress then tailoring the synthetic world accordingly. Finally, MR is a mixture of real and virtual, such as the real roads of a city and a newly planned architectural building design, in order to test its match to the environment before ever built, or a game designed to provide an environment to new students to learn the city geography and topology, in which, the player interacts with different imaginary creatures roaming the city streets.