Thiel was raised on a farm in southwest Minnesota, near her birthplace of Adrian, Minnesota. Her parents grew up in immigrant farm families and each had completed an eighth grade education. Thiel herself attended a private elementary school nearby her farm in Lismore, Minnesota, for grades 1-8 and public high school in Adrian, Minnesota for grades 9-12. Support from the National Merit Scholarship Program enabled her to attend Macalester College in St. Paul, Minnesota, where she was inspired by her freshman chemistry course and its instructor, Prof. Emil Slowinski to major in chemistry. She completed a BA in chemistry with a minor in mathematics in 1975. After working for a year at Control Data Corporation as an analytic chemist, she enrolled in the chemistry department at the California Institute of Technology, with financial support from a National Science Foundation Predoctoral Fellowship. She completed a PhD in chemistry in 1981 under the supervision of W. Henry Weinberg.
