You will be given a definition of a task first, then some input of the task.
In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

For this reaction to occur, components occupying the Gamow window must tunnel through the Coulomb barrier. When elements heavier than iron are used in this process, a net energy absorption occurs. Attempts have been made to run current through contained plasma fuel for this process in toroidal magnetic chambers such as stellarators and [*] tokamaks. The proton-proton chain and the CNO cycle are two kinds of this process by which stars turn hydrogen into helium, and Fleischmann and Pons did not actually discover a "cold" version of this process. For 10 points, identify this process by which several small atomic nuclei combine to form a larger one.
Output:
Science