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.
A berm is a raised strip of ground that runs along the side of a road or a body of water. You might stand on the berm by a lake with your fishing pole as you bait your hook. A berm is any stretch of grass or land that forms a kind of shelf above or along a river, train tracks, or highway. Some berms are a natural feature of the landscape, while others are man made.