A massive nuclear fusion experiment just hit a major milestone, potentially putting us a little closer to a future of limitless clean energy.

Japan's JT-60SA is now the biggest tokamak to reach "first plasma" anywhere in the world.

On October 23, the National Institutes for Quantum Science and Technology announced that it had achieved “first plasma” at the JT-60SA, meaning the device was used to create and contain a super-hot plasma for the first time — a milestone in the development of a tokamak.

Stepping stone: At 52 feet tall, the JT-60SA is now the biggest tokamak to reach first plasma anywhere in the world — but it likely won’t be for long.

The JT-60SA tokamak is being built to support ITER, an under-construction tokamak twice as tall. Once that device achieves first plasma — currently scheduled for December 2025 — it’ll become the largest nuclear fusion device to fire up.

While fusion projects rarely go quite as planned, the hope is that ITER will be the device that finally proves commercial fusion power is possible — ushering in a new era in clean energy.