Geoff received his Ph.D. from Cornell University in 1991, and after a postdoc with IBM Research, joined the Physics & Astronomy faculty at Dartmouth College. He first became interested in modeling in the mid-1990s through the papers of David Hestenes and coworkers. At the time, ten years before the founding of the American Modeling Teachers Association, there was no clear path for teachers to become trained in Modeling Instruction. In 2001 he moved to Dupont Central Research and Development in Wilmington, Delaware. At Dupont he worked on organic molecule semiconductors, flexible solar cells, and printable thermoelectric materials, among other interesting systems. In 2016 he left Dupont to teach physics at St. Joseph’s Preparatory School in Philadelphia, and took the first of several Modeling workshops. In 2025 he retired from the classroom, but not from his interest in, and passion for, teaching and learning physics.