Final answer:
Nuclear fusion is the process where light nuclei overcome electrostatic repulsion through kinetic energy, combine to form a heavier nucleus, and release energy.
Step-by-step explanation:
The question pertains to the sub-atomic process that occurs during nuclear fusion. This phenomenon can be represented by two light atomic nuclei, such as hydrogen isotopes, coming close enough so that nucleic forces overcome their electrostatic repulsion.
The nuclei then combine to form a heavier nucleus, like helium, releasing a tremendous amount of energy in the process. To illustrate at the sub-atomic level: Picture two positively charged nuclei approaching each other, their repulsion resembling a hill that they must climb.
Once they gain sufficient kinetic energy, possibly from high temperatures, they overcome this hill and fall into a potential well, merging into a larger nucleus, such as helium, and releasing energy as observed in stars like the Sun.