Nuclear fusion releases energy when light nuclei combine into heavier ones. The central engineering challenge is creating and controlling the extreme conditions needed for fusion often enough, efficiently enough, and cheaply enough to make a power system.
Two major approaches
Magnetic-confinement systems use magnetic fields to hold hot plasma, while inertial-confinement systems rapidly compress a small fuel target. The National Ignition Facility uses powerful lasers to implode a tiny target containing fusion fuel.
The ignition milestone
NIF first achieved fusion ignition in December 2022. Since then, ignition has been repeated. In April 2025, NIF produced 8.6 megajoules of fusion energy from 2.08 megajoules of laser energy delivered to the target, a target gain above four. In June 2026, NIF reported another ignition shot with a measured yield of 7.9 megajoules.
What remains unsolved
Practical fusion energy still requires repetition rate, target manufacturing, component durability, tritium fuel management, heat capture, electricity generation, maintenance, economics, and a full plant that produces more usable energy than it consumes over sustained operation.
Why the milestone still matters
Ignition shows that laboratory fusion plasmas can enter a regime in which self-heating becomes strong enough to amplify the reaction. That is a major physics achievement. The next challenge is transforming the physics milestone into an engineered energy system.