What is the Difference Between Nuclear Fusion and Fission?

9. Efforts to Achieve Nuclear Fusion

Achieving a sustainable fusion reaction has been a much rockier path than the fission efforts of the 1940s. This is due to a fundamental barrier engineers face, which is how to overcome the electrostatic repulsion between atoms and force them to fuse without expending more power than is gained. In nature, this is achieved in a regime of extremely high temperatures, on the order of millions of degrees. Many decades and billions of dollars have been spent around the world, and it is still unclear when, if ever, a functioning nuclear fusion power plant will become operational.