The plunge freezer is used to most rapidly deep-freeze small amounts of solutions with the structures contained therein, e.g., viruses or exosomes in a way that amorphous ice is formed. Thereby samples on special grids which are frozen at below -165°C with help of a cryo transfer system are introduced into the transmission electron microscope. Here we can examine the untreated specimen which is free of fixation and contrasting artefacts, which, however, has a considerably lower contrast.