A tokamak is a device with a unique mission: producing the tremendous temperature and pressure conditions needed for nuclear fusion to take place. Developed in the Soviet Union in the 1960s, it consists of a doughnut-shaped vessel surrounded by powerful magnets. Deuterium and tritium fuel inside the tokamak are heated to 150 million degrees Celsius (270 million degrees Fahrenheit) – ten times hotter than the Sun’s core! These extreme temperatures cause the fuel’s atoms to separate into ions and electrons, forming a cloud of charged particles known as plasma. To maintain the fuel’s temperature, it cannot be allowed to touch the cooler walls of the tokamak – besides, at this temperature the plasma would simply melt through any solid material known to man. Instead, two sets of magnets create an invisible cage, confining the fuel and suspending it safely away from the tokamak’s walls. The Joint European Torus, or JET (pictured), is currently the world’s largest nuclear fusion reactor using a tokamak, though construction of its successor – the International Thermonuclear Experimental Reactor (ITER) – is already underway.