Scientists in Northern California have done it again, producing a net gain in a fusion reaction for only the second time ever in a lab. A net gain occurs when the energy output of a fusion reaction is greater than the power it took to create the reaction in the first place. Lawrence Livermore Lab achieved the feat back in December using more than 200 lasers to create the reaction. But lab officials report on Sunday that this latest experiment produced even more energy than the first. The Department of Energy calls it a massive breakthrough in the development of clean power.