The author describes very briefly certain fundamental characteristics of the earth-orbital environment which make a manned space station attractive for research in sciences and engineering. Description is given only for selected features that are both unique and important: Agravic Force Field, Hard Vacuum, Cosmic Radiation, and Spatial Disposition. Description of facilities, equipment, general purpose laboratories, and experimental hardware is left to other authors or to other media, including referenced studies. Several references are given. These in turn will provide the interested reader with comprehensive information and further references in depth.