The US is taking definitive steps toward nuclear fusion, with plans to build its first plant by the 2040s.

Nuclear fusion represents the Holy Grail of energy production. Unlike nuclear fission, fusion involves combining atoms rather than splitting them apart. Fusion is cleaner than fission, producing helium as a byproduct, rather than radioactive waste. There is also minimal chance of the kind of explosive chain reaction that can occur when ripping atoms apart. Deuterium — the primary fuel used in fusion — is distilled from sea water, unlike the rare-earth elements used in fission.

Despite its advantages, there are still many hurdles to overcome. Chief among them is developing a method that produces substantially more energy than the cost of fusion.

A group of US scientists believe they can overcome the challenges, and have set the 2040s as their goal for establishing the first power plant in the US, according to Science.

“The community urgently wants to move forward with fusion on a time scale that can impact climate change,” says Troy Carter, a fusion physicist at the University of California, Los Angeles. “We have to get started.”