Zyklon B is a pesticide that was originally developed for fumigating buildings and ships. It contains hydrogen cyanide, a highly toxic gas. During World War II, it was infamously used by the Nazi regime in extermination camps as a method of mass murder. The use of Zyklon B in gas chambers led to the deaths of millions of people, primarily Jews, during the Holocaust. Its association with these atrocities has made it a symbol of the horrors of genocide and the consequences of unchecked hatred and discrimination.