The world's strongest laser - powerful enough to create conditions as hot as inside the Sun - was unveiled Friday in the western U.S. state of California for an audience of politicians and scientists.
The stadium-sized National Ignition Facility actually houses 192 lasers that all point towards a tiny blob of hydrogen.
When the lasers shoot, scientists expect the hydrogen will fuse into helium, a chemical reaction like what makes stars burn and nuclear bombs explode.
The project began in 1997 and cost the federal government an estimated $3.5 billion. The government says it will allow scientists to study in a lab what happens in a nuclear explosion. They say it will help scientists assess the safety of the aging U.S. nuclear arsenal.
But critics say the laser is unnecessary and costly. Some also worry it could help develop new nuclear weapons.
Proponents of the giant laser say there is another possible benefit. They say they hope to create a fusion reaction called "fusion ignition." This reaction could create huge amounts of electricity.
Scientists suggest such reactions could lead to a new green energy source, and eliminate the current dependence on fossil fuels.
California governor Arnold Schwarzenegger hailed the laser as a breakthrough for his state. The unveiling was attended by around 3,500 people.
Scientists say they plan to begin experimenting with fusion ignition by next year.
Some information for this report was provided by AFP and AP.