The team measured the magnetic activity by sending an electron beam along the field lines, and then using a fluorescent rod to sweep through those lines and create light in the shape of the fields. As you can see above, the result is a very scientific take on light painting.

W7-X isn't a power plant. However, confirming the nature of its magnetic fields will help prove the viability of stellarators as templates for future fusion reactors. While that means that any practical machine is likely many years away, there's at least a good reason to be patient. Stellarators promise to be safer than existing tokamak reactors, which could spark a crisis if their current fails or something disturbs their magnetic fields. Ideally, you'll get a tremendous power source that's both cleaner and safer than nuclear energy.