Virtual Environments allow users to interact with virtual worlds, but usually these interactions are in front of a monitor or a projected wall. Augmented Reality brings the feeling of reality to these interactions. The user can combine the virtual world with the virtual world. Interact and feel the objects, together with artefacts that are generated by a computer. This article provides an overview and introduction to the problems of Augmented Reality systems and shows the state of the art in current technological developments. The usability bottlenecks of existing systems and probable solutions are also discussed.