As with most instructors, I have a problem with microscopy students. Quite often when viewing an EDS X-ray spectrum there will be a small peak at 2 times the energy of the main peak. My students will say, “What peak is that?” I will say, “It's a sum peak.” “We know it's some peak, but which one?” “A sum peak,” I say. Frustrated, they respond, “We know it's some peak…and stop talking like Lawrence Welk!” Can you help me?