Helion Energy develops magneto-inertial fusion generators that produce electricity through pulsed magnetic compression of deuterium-helium-3 plasma, reaching temperatures over 100 million degrees Celsius and directly recapturing energy without a steam cycle. Its prototypes include Trenta, which hit 100 million degrees C in 2021, and Polaris, operational since late 2024, which achieved 150 million degrees C and deuterium-tritium fusion in 2025. The company sells clean electricity via long-term power purchase agreements to customers like Microsoft, which signed for 50 megawatts by 2028, and Nucor, targeting a 500-megawatt plant by 2030 to power steel mills. In January 2025, Helion raised $425 million in an oversubscribed Series F round with investors including Lightspeed Venture Partners, SoftBank Vision Fund 2, Sam Altman, and Nucor. Co-founder and CEO David Kirtley leads the company, headquartered in Everett, Washington, where it broke ground on its first commercial plant, Orion, in Malaga, Washington, in July 2025.