This tag should be used for the 1972 Isaac Asimov novel "The Gods Themselves" or one of its serially-published parts.
The Gods Themselves is a science fiction novel written by famous SF author Isaac Asimov, published in 1972. It was originally serialized in three parts (parts 1 and 3 in Galaxy magazine, part 2 in Worlds of If magazine) earlier that year.
The plot centers on the inhabitants of a parallel universe with physical laws that differ from our own, and the threat posed to our Sun caused by their attempts to extract energy from our universe. The story is notable for its depiction of an alien species with more than two reproductive sexes.