The stellarator that took 19 years to build is seen as a path to virtually limitless sources of zero-carbon electricity.

The world’s largest nuclear fusion reactor has been switched on in Germany.

It took 19 years to build but it is hoped that the biggest and most complex stellarator of them all, the Wendelstein 7-X, will pave the way for virtually limitless sources of zero-carbon electricity.

Al Jazeera’s Neave Barker reports.