Interview with Stephen Seltzer, retired from the National Institute of Standards and Technology where he was Leader of the Dosimetry Group in the Radiation Physics Division. Seltzer discusses his current interests in photoelectric cross sections and he explains why NIST supports research in radiation physics. He recounts his childhood in the Washington DC area, he describes his education at Virginia Tech and his first job at the National Bureau of Standards. Seltzer describes the advances in ionizing radiation at NIST during his junior years and the formative mentorship provided by Martin Berger and his pioneering work in radiation science and Monte Carlo calculations. He explains why Monte Carlo codes provide a solution to the Boltzmann Transport Equation and why electron transport research provides value to space exploration and how NIST contributed to proton therapies for cancer. Seltzer discusses his administrative service as leader of the Radiation Interactions and Dosimetry Group, and he explains his motivations to serve as a mentor to younger colleagues at NIST. At the end of the interview he reflects on the budgetary environment at NIST over his tenure and why young physicists should consider NIST as an excellent place to pursue a career.