In this interview, David Zierler, Oral Historian for AIP, interviews Claudio Pellegrini, professor emeritus of physics at UCLA. Pellegrini describes his childhood and education in Italy, and his research at the Frascati Lab in Rome, where he built a diffusion cloud chamber to do an experiment on photoproduction using an electron synchrotron. Pellegrini describes his graduate work at the University of Rome, his work at the Institute for Theoretical Physics in Copenhagen, and the circumstances leading to his work as a visiting scientist at Berkeley National Laboratory. Pellegrini describes his initial work at SLAC in 1965 and his growing interest in free-electron lasers in the mid-1970s during his work back at Frascati, and his decision to begin work at Brookhaven on the National Synchrotron Light Source. Pellegrini discusses his research and the lab he built at UCLA, where he worked on instability theory among other projects. In the last part of the interview, Pellegrini describes his recent work at SLAC, where he has continued his work in x-ray free-electron lasers, and he shares his ideas on what the past 400 years of scientific advances might tell us about discoveries in the future.