At the start of the tokamak revolution, there was a huge proliferation of different designs for tokamaks from universities and establishments around the world - but gradually, as it became clear that making progress would require larger and larger machines, these efforts broadly ended up concentrated in three main devices. The Joint European Torus (JET) in the UK, the JT-60 in Japan, and the Tokamak Fusion Test Reactor (TFTR) in the US. www.physicspodcast.com