MEDSEM satisfies NASA's stated need for new and innovative scientific measurements for in situ planetary exploration. To date, although miniaturizing scanning electron microscopes has been a "holy grail" for developers of planetary instruments, an in situ electron microprobe instrument has never flown. Once successfully demonstrated, MEDSEM would be a strong candidate for planetary instrument payloads for NASA's future landed missions, as described by the National Research Council Committee on the Planetary Science Decadal Survey for future NASA missions from 2013 2022. According to the Decadal Survey, primary planetary targets for landed missions include the moon, Mars, Venus and Europa. In the field of materials science and engineering outside of NASA, there is a great need for capable, field-portable instruments that are rugged and reliable. As with NASA missions, size, weight and power consumption are of concern for humans transporting these instruments into remote locations for geological studies, environmental monitoring and oil exploration. An added concern is the overall cost of the instrument, especially for widespread acceptance and use. A successful MEDSEM instrument would open up numerous applications in the educational arena. At both the K-12 and college level, MEDSEM could be used for science demonstrations as well as for hands-on experimentation and research in chemistry, solid-state physics, geology and materials science laboratories. Although MEDSEM cannot match the spatial resolution of terrestrial laboratory instruments such as scanning electron microscopes (mm vs nm), still it could serve as a rapid screening device with the ability to answer basic composition-related questions. MEDSEM's primary advantage, of course, is its ability to simultaneously make multiple, different measurements on the samples being studied in ordinary room air. It is anticipated that MEDSEM will continue to evolve as an instrument, incorporating the latest advancements in micro- and nanotechnology.