The first electron microscope in Costa Rica was a donation from the government of Japan throught its International Cooperation Agency (JICA) in 1974. This donation made possible the consolidation of what was to hecome the University of Costa Rica's Electron Microscope Unit (UME). Within three years the first scientific papers were published, dealing with ultrastructural aspects of "Com's rayado fino virus" and rotavirus, viral agent of human diarrhea. Subsequent papers out of the UME were published for the most part in the Journal of Tropical Biology, totaling at least 50 in that journal alone by the year 2000. With the recent acquisition of Energy Dispersive Spectrometer to coupled in transmission electron microscope and scanning electron microscope to X ray analysis, the data acquisition of the UME has been greatly enhanced, making possible to analyze both structure and elemental chemical composition in a specimen. Other applications of this new technology include studies of environmental pollution with heavy metals, such as comparative analysis of residues on leaves from urban areas and those on leaves from primary forest.