In 1990, the German Democratic Republic ceased to exist almost overnight, as did its Ministry for State Security, the Stasi. During two years of research, Berlin-based artist Simon Menner delved deep into the its archives. His photo book "Top Secret" gives a unique insight into the state authority's surveillance work. This image is part of a "disguise seminar" for Stasi employees.

This image is part of a surveillance film. One person would be shadowed for days. And each image would be marked with a small arrow showing the person. The Stasi employed about 90,000 full-time employees and about 100,000 unofficial employees. The Stasi is considered to be one of the most close-knit spy networks and most effective secret police agencies of the time.

Spying is ultimately a craft. Reenactions like this are found quite often in the Stasi archives. They were used to train Stasi spies by improving their observation skills and attention to detail: when, where, who was the suspect meeting?

And what is the suspect reading? This photo, again taken for training purposes, presumably uses a book from the Stasi's own libary. The book shown on the photo is titled "The ABC of money, power and wealth in the Federal Republic." It was written by West German author Bernt Engelmann, who, as it turned out after German reunification, had been a paid Stasi informer.

Special emphasis was placed on the written correspondence of suspects under surveillance. By the way: everyone who is recognizable on the images in Simon Menner’s book is a former Stasi employee. Everyone else has been blurred to make them unrecognizable for readers.

This reenaction shows the extent of the Stasi's surveillance mania in a single object: the Stasi would photograph every single person who approached this mailbox. Other images show people in civilian clothes emptying the boxes after finishing the observation. Later, each letter was filed along with the photo of the person who had dropped it in the mail slot.

This Polaroid photo shows how precisely the Stasi operated. It was taken before a secret apartment search - so that the room could be left exactly as it was found, down to the last detail. "I struggled with myself over whether I wanted to use such images in my book," admits Menner. "But in the end, the people from the archive and I agreed that it is important to show such images as well."

This model airplane was also photographed during a secret search, along with Western magazines, cigarettes and whiskey bottles. Why the object was considered suspicious leaves room for speculation: Did the Stasi think the owner of the toy could be planning to escape to West Germany? As bizarre as it looks: thinking about escape was a serious offence and was harshly punished.

Around 25 million presents of food and clothing were brought from the West to East Germany every year. Stasi members opened each shipment, and the content of the shipment was photographed and often partially confiscated. Many of the presents never reached their addressees.

This is probably one of the strangest images amongst all the photos in the book. At a Stasi member’s private birthday party, the spies dressed up as their victims - as artists, church dignitaries or athletes.

The Stasi members demonstrated their peculiar sense of humor by carrying out mock knighting ceremonies. The medal in this case - a telephone handset - honors an agent for his particularly good telephone spying. This private photo also landed in the archive. The Stasi's desire to collect everything even went as far as archiving the scents of targets.

Some images from the Stasi archive still remain a mystery. This image of a dead swan was found in Erich Mielke's office after German reunification. He was the East German Minister of State Security from December 1957 to November 1989. "Some photos just have to be accepted as they are - in all their absurdity and strangeness," concludes Simon Menner.