Microsoft has signed a power purchase agreement with nuclear fusion energy startup Helion for at least 50 megawatts of electricity beginning in 2028, the companies announced Wednesday.

Why it matters: The agreement is being billed as the world’s first such deal for a fusion firm. It comes as money and interest pours into the much heralded, yet-to-be-realized clean energy source.

Zoom in: Helion plans to locate its fusion plant in Washington state, home to both companies, and sell power directly into the grid via Constellation.

Microsoft plans to use the electricity to power its data centers, chief sustainability officer Melanie Nakagawa told Axios in an interview.