Sci Fi (or science fiction) genre stories involve strong elements of technology that are explained with thorough details and are plausible (when based on hardcore science facts and proof, sci fi becomes hard science fiction). In general, the stories center around the effects and ramifications of computers and machines. Sci Fi stories can involve traveling through space, time, or alternate universes, as well as, involve alien life-forms.
Hardcore science like DNA tampering/restructuring (i.e. genetic engineering) or other such medical experiments are included in the Sci Fi Genre, too. This can lead to Sci Fi boarding on the suspense, thriller, or horror genres, especially with the experiments go wrong.