Abstract
Today's high-performance electron microscopes have achieved an optical resolution below 0.2 nm. The radiation sensitivity of biological specimens inhibits structure analysis with a corresponding resolution, thus several attempts are being made to reduce the electron dose impinging on the specimen to an amount which is physically unavoidable. Development trends are toward higher voltages, correction of aberrations in the lower energy range, application of image reconstruction methods, and low specimen temperature. The technical state of the various components of conventional transmission electron microscopes is assessed, i.e. beam sources and condensers, objective and imaging systems, specimen stages, image-recording and image-processing devices, and energy-filtering systems. Properties of commercial instruments are described, and non-commercial high-resolution projects now under way are mentioned.