Following the fall of the Berlin Wall in 1989, the headquarters of the Stasi (the East German secret police) were found to contain a large room in which many thousands of "smell jars" were stored.
Each jar contained an odour sample from a suspect, collected either during interrogation, by means of a perforated iron smell sample chair, or by breaking into the suspects' homes and stealing their dirty underwear.
The smell samples were collected so that released suspects could be found for further interrogation at a later date. Stasi agents would then retrieve the suspect's sample, and give it to their sniffer dogs.
The collection of a smell sample is depicted in The Lives of Others
(2007), the first two scenes of which are embedded below. In the opening scene, Stasi captain Gerd Wiesler interrogates someone who is suspected of helping a friend defect. Afterwards, in a lecture, he describes Stasi interrogation methods, and how the smell samples were collected.