In a world with an ever-increasing demand for electricity and a deteriorating environment, Chinese scientists are leading the charge to develop what some see as the holy grail of energy.
The BBC's Stephen McDonell was given rare access to their facility in Anhui province.
Imagine limitless energy with virtually no waste at all: this is the lofty promise of nuclear fusion.
On Science Island in Eastern China's Anhui Province, there is a large gleaming metal doughnut encased in an enormous shiny, round box about as big as a two-storey apartment. This is the Experimental Advanced Superconducting Tokamak (or EAST).
Inside, hydrogen atoms fuse and become helium which can generate heat at several times the temperature of the sun's core.
Powerful magnets then control the reaction, which could one day produce vast amounts of electricity if maintained.
Around the globe, they are trying to master nuclear fusion - in the United States, Japan, Korea, Brazil and European Union - but none can hold it steady for as long as the team in Anhui.
Right now that's 100 seconds and it gets longer every year. Here they're already talking about goals which are 10 times as long, at temperatures of 100 million degrees Celsius.
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