Feynman had studied the ideas of John von Neumann while researching quantum field theory. His most famous lecture on the subject was delivered in 1959 at the California Institute of Technology, published under the title "There's Plenty of Room at the Bottom" a year later. In this lecture he theorized on future opportunities for designing miniaturized machines, which could build smaller reproductions of themselves. This lecture is frequently cited in technical literature on microtechnology, and nanotechnology. Feynman also suggested that it should be possible, in principle, to make nanoscale machines that "arrange the atoms the way we want" and do chemical synthesis by mechanical manipulation. He also presented the possibility of "swallowing the doctor", an idea that he credited in the essay to his friend and graduate student Albert Hibbs. This concept involved building a tiny, swallowable surgical robot.