Electron microscopes have certain advantages over optical microscopes: The biggest advantage is that they have a higher resolution and are therefore also able of a higher magnification (up to 2 million times). Light microscopes can show a useful magnification only up to 1000-2000 times. This is a physical limit imposed by the wavelength of the light. Electron microscopes therefore allow for the visualization of structures that would normally be not visible by optical microscopy.
berm (plural berms) A narrow ledge or shelf, as along the top or bottom of a slope. A raised bank or path, especially the bank of a canal opposite the towpath. A terrace formed by wave action along a beach. A mound or bank of earth, used especially as a barrier or to provide insulation.
Also, berme. Fortification. a horizontal surface between the exterior slope of a rampart and the moat. 2. Also called bench. any level strip of ground at the summit or sides, or along the base, of a slope. 3. Also called backshore, beach berm. a nearly flat back portion of a beach, formed of material deposited by the action of the waves. 4. Chiefly Indiana, Ohio, Pennsylvania, and West Virginia. the bank of a canal or the shoulder of a road.