The development of a fusion reactor to generate clean energy has long been the holy grail of scientists worldwide. Researchers are now boasting of advances that could make the technology achievable in the near future, and private investors are taking notice.

“Fusion has been talked about for many years, and it disappointed a lot of people,” says Jaeyoung Park, president and chief scientist at EMC2, a California company that is hoping to tap private investment capital to support its fusion research. “Now we’re on the other side of it. With all the technologies available now, it has become a great time to do fusion research.”

Nuclear reactors produce electricity by splitting atoms, the process known as fission. Fusion is the process by which two atoms combine and—illustrative of Albert Einstein’s famous equation, E=mc²—release energy by converting mass into energy. Fusion powers the sun, all the other stars and just about everything else in the universe. “Fusion is a nearly ideal energy source—essentially inexhaustible, clean, safe and likely available to all nations,” wrote Steward Prager, the Princeton Plasma Physics Laboratory’s director, in a New York Times post.

At a time when energy demand is increasing and concern about climate change is growing, power stations that use fusion would have several advantages, according to the Culham Centre for Fusion Energy, the U.K.’s national fusion research laboratory.

There would be no carbon emissions. Energy production would be efficient: One kilogram of fusion fuel could provide the same amount of energy as 10 million kilograms of fossil fuel. These power stations would also be safe because the small amount of fuel used would mean a large-scale nuclear accident could not happen. And fusion power plants should supply large amounts of electricity, costing broadly the same as other energy sources, according to estimates.

EMC2 has been conducting U.S. Navy-supported research for two decades on a reactor called the polywell, which combines two fusion technologies: electron beams to heat plasma to 100 million degrees and a magnetic bottle to confine the hot plasma. According to a Navy review, the company’s scientists have validated these ideas, and next they must demonstrate that the technologies can support a fusion reaction—the last step before possible commercialization in the form of an electricity-producing reactor.

In October, Lockheed Martin announced a breakthrough of its own, stating it has figured out how to harness fusion energy.

Several other approaches to controlled fusion are also being tested.

The International Thermonuclear Experimental Reactor (ITER) project in France, which is expected to cost more than $20 billion and be completed around 2030, is intended to serve as a bridge, establishing the scientific basis for the first commercial fusion power plant that could be built in the 2040s for the large-scale production of electricity. The project is reportedly receiving funding from the U.S., the European Union, South Korea, Japan, China, India and Russia.