It has been understood since the days of Ernst Abbe that an optical microscope can reach higher resolution the wider the set of angles from which it can observe the specimen — this angular range, of course, is what is indicated by the Numerical Aperture (NA) of the objective lens. Over more than a century of objective lens development, this light collecting angle has been increased closer and closer to the full 180° angle available above a microscope slide. There is, however, a second, equally large and easily accessible set of observation angles available on the other side of the specimen slide, and a standard microscope makes no use whatsoever of light emitted in these directions. One might then ask whether there is not a substantial resolution advantage to be had by devising a microscope that does make use of this "back side" light. The answer, in fact, is yes.