One of the world's biggest science experiments is being threatened by rising costs, delays and technical challenges.
The Iter project was set up three years ago to build an experimental nuclear fusion reactor in the south of France.
But construction costs alone have more than doubled and some scientists now argue that the development of fusion as a commercial power source is still at least 100 years away.
The BBC's Matt McGrath was shown the site by Iter's communications manager Neil Calder.
Bookmark with:
What are these?
E-mail this to a friend