In fusion reactions, hydrogen isotopes meld together, creating high-energy alpha particles. The key to increasing the captured energy was to keep these particles trapped inside the container, feeding energy back into the reaction.
To make fusion a viable renewable energy source, scientists still have work to do: Some of the lasers’ energy was lost before even making it to the tiny bead. The energy produced needs to increase at least a hundredfold for the total energy it takes to turn on a fusion reaction to be less than the total energy gained. Still, this is a spark.