This time, the long-promised advent of an abundant, safe, low-carbon and affordable energy source seems closer than ever. This hope lies in a nuclear reaction that has been known since the 1930s: fusion. In this reaction, light atomic nuclei merge to release new, highly energetic particles. This is how stars shine and how hydrogen bombs detonate.

Nuclear fusion is the opposite of nuclear fission, which splits uranium nuclei in nuclear power plants to release energy and generate electricity. Since humans lack the Sun's immense mass to force atoms to merge and do not want to blow up the planet to power it, physicists and engineers have competed to control this energy for over 70 years. Every decade, they promised that the Holy Grail would be achieved in 10 years.

The landscape is shifting, with a wave of companies now determined to deliver. At least 53 are in the game today, compared with 10 just 15 years ago, according to the latest report from the Fusion Industry Association (FIA), a lobbying group created in 2018. Roughly $9.7 billion (€8.2 billion) has been invested in the sector up to July 2025, including $2.64 billion in the previous 12 months alone – compared to less than $2 billion in total before 2021.

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