  From its invention in 1997, the Gas Electron Multiplier has been applied in
nuclear and high energy physics experiments. Over time however, other
applications have also exploited the favorable properties of GEMs. The use of
GEMs in these applications will be explained in principle and practice.
  This paper reviews applications in research, beam instrumentation and
homeland security. The detectors described measure neutral radiations such as
photons, x-rays, gamma rays and neutrons, as well as all kinds of charged
radiation. This paper provides an overview of the still expanding range of
possibilities of this versatile detector concept.
