A Tour of the Cell Modern electron microscopes have a resolving power of about 0.2nm. Enhanced resolution and magnification allowed researchers to clearly identify subcellular organelles and to study cell ultrastructure .
Image is focused onto a viewing screen or film.
Used to study internal cellular ultrastructure. Electron beam scans the surface of the specimen usually coated with a thin film of gold. Scanning beam excites secondary electrons on the sample's surface. Secondary electrons are collected and focused onto a viewing screen. SEM has a great depth of field and produces a three-dimensional image.