The presentation will be a simple introduction to classical stable isotope effects and mass-independent isotope effects (and their potential causes), followed by an introduction to sulfur isotope cosmochemistry. My reasearch is focused on sulfur isotope measurements of troilite (FeS) nodules in iron meteorites, it appears that the two main different "genres" of iron meteorites have different degrees of mass independent sulfur enrichment. I will attempt to explain these differences and their implications for sulfur isotopic evolution of the early solar system.