German scientists today will set about the first steps towards what has become the Holy Grail of energy—nuclear fusion, which has the potential for unlimited amounts of clean power. There are a number of challenges to harnessing this power—researchers need to build a device that can heat atoms to temperatures of more than 100 million °C (180 million °F).

After almost nine years of construction work and more than a million assembly hours, researchers from the Max Planck Institute in Greifswald are set to do just that by heating a tiny amount of hydrogen until it becomes as hot, hopefully, as the center of the Sun.

Researchers are keen to tap into the incredible amount of energy released when atoms join together at extremely high temperatures in the super-hot gas known as plasma. Today’s test will not produce any energy, just the plasma—a different state of matter created at extremely high temperatures. German chancellor Angela Merkel, who has a doctorate in physics, will reportedly attend.

The Wendelstein 7-x is the largest stellarator fusion device in the world—dubbed the “dark horse in fusion energy research” and costing €370 million ($404 million) to build—rivalling the standard tokamak fusion reactor that was developed by Soviet researchers. Researchers were able to carry out the first successful experiment last year, producing helium plasma. Satisfied with the initial results, researchers are setting out to work to produce the first plasma from hydrogen.

Scientists are still many years away from producing a clean and safe form of nuclear power and there have been plenty of setbacks. In the last 60 years, scientists have failed to create a fusion reaction that makes more energy than it consumes.

The international coalition behind a rival, multibillion-dollar ITER fusion project, which aims to show that nuclear fusion is technically feasible, recently announced it would take six years longer than planned to build their device—and require a lot more funding.