The course deals with advanced topics in stable and radiogenic isotope geo-/cosmochemistry and builds on Ge 140 a and b, with emphasis on non-traditional isotope systems (Mg, Fe, Ti, Mo, U, etc.). Starting with close examination of seminal papers, each topic will build up to a discussion of the remaining outstanding questions. Topics to be covered will be guided by class interests. Example subjects could include: the early solar system, nucleosynthetic anomalies, the early Earth, planetary differentiation, paleoredox reconstructions, medical use of stable isotopes. Given sufficient enrollment (~5 or more), course format will follow a "Role playing paper-reading" style (https://colinraffel.com/blog/role-playing-seminar.html). Grades will include participation, intellectual contribution to updating the content of the periodic table of stable isotopes, and the writing by the whole class of a scientific review/original paper (with the goal of submitting it for publication).