The eye is the most important human sensory organ. It supplies more information to the brain than any other sensory organ, but the resolution of the human eye is limited. However, many interesting objects or their structures are too small to be recognised with the naked eye. For example, light microscopes are used to view a cell, the building block of life. This allows structures as small as 1 µm (1 thousandth of a millimetre) to be imaged. For imaging even smaller details, such as the inner structure of cell organelles or the structure of crystals made of atoms, conventional light microscopes cannot be used for physical reasons. Electron microscopes are used for this purpose, as they have a much higher resolution than light microscopes.

If you want to observe the surface structure of such small objects non-destructively, you can use a scanning electron microscope. This enables detailed imaging of surfaces with a resolution in the nanometre range (1 millionth of a millimetre) and a depth of field up to three hundred times greater than that of a light microscope. A scanning electron microscope can achieve magnifications of up to twenty thousand times, which represents an enormous increase in performance compared to a light microscope with a magnification of between six and a thousand times and allows the experimenter to recognise and examine ultrastructures. In addition, an EDX (energy dispersive x-ray) device enables elemental analysis, i.e. an analysis of the elements that make up a sample. In contrast to light microscopy, in which the sample to be examined is illuminated by a light source with a broad spectrum of colours, scanning electron microscopy uses an electron beam to generate images, which is focused by electromagnetic lenses and scans or "scans" the surface of the sample object point by point and line by line. This creates the three-dimensional impression typical of scanning electron microscope images. This method is used in biological and medical fields or in material science and forensic investigations.

Transmission electron microscopes are very similar in principle to light microscopes, as in both methods the object under investigation is irradiated by light or electrons. For this purpose, the object must be correspondingly thin. The object to be examined must therefore be embedded in a medium (usually an acrylic resin) and is usually cut into thin slices on the ultramicrotome using a diamond knife. The slices, which are attached to a carrier plate, are first coloured to increase the contrast and can then be examined under a microscope. The highly magnified image appears simultaneously on a fluorescent screen and can be recorded by a digital camera. With such transmission electron microscopes, distances of less than 0.2 nm (1 five millionth of a millimetre) can be visualised today. This size corresponds approximately to the diameter of a single atom. Electron microscopy can therefore also be used to visualise the atomic structure of crystals.