The Stasi was an Eastern Germany version of the KGB, established by the Soviets in 1952. Just like the KGB, the Stasi was mostly busy looking for enemies of the people, employing round-the-clock surveillance, and eavesdropping on German citizens. After the fall of the Berlin Wall, people assaulted the Stasi headquarters, dissolved the organization, opened its archives to the public, and created a museum in the main building.

Stasi Museum 

On the evening of January 15th in 1990 demonstrators took possession of the headquarters of the Ministry for State Security (MfS) in Berlin-Lichtenberg. The Berliner Bürgerkomitee (Berlin Committee of Citizens) started here the closure and disorganisation of the MfS. One week later the Zentrale Runde Tisch (The Central Round Table) decided that a memorial place and research centre should be established in the former House No. 1 in the Stasi-Headquarters.
The new government of the GDR, formed after the elections on March 18th in 1990, made on May 16th a decision to establish the memorial place and research centre, but it was not realised as the responsible ministries were suspended when both states in Germany reunited.

The website of the Stasi Museum is https://www.stasimuseum.de/en/enindex.htm

An extensive photo essay by Egor Egorov can be found at https://egorfine.livejournal.com/464589.html

Here are a few samples of the photos by Egor Egorov.

Camera disguised as a button.

Camera disguised as a button.

 

Camera hidden in tree trunk.

Camera hidden in tree trunk.

 

Watch microphone and recorder

Wristwatch microphone and recorder