Postdoctoral Fellows and Researchers Postdoctoral fellows (PDFs) come to the School of Arts and Sciences for further training in their chosen discipline. An individual who has been designated as a PDF receives training, where s/he is working under the supervision of an established faculty member who serves as a mentor. As dictated by the nature of the program, the fellow may be undertaking scholarship, research, service, and/or teaching activities, all of which provide training essential for career development. Because education is a pre-eminent mission of SAS and because PDFs are professionals in training, it is important that the programs for postdoctoral fellows are designed to advance their careers, in addition to contributing to the mission of the department which they are working.