In 1983, the physicist Mordehai Milgrom initiated a new research program in cosmology, called MOND (for MOdified Newtonian Dynamics), or Milgromian dynamics. In three papers, Milgrom proposed a set of postulates describing how Newton’s laws of gravity and motion should be changed in regimes of very low acceleration. Milgrom’s postulates were designed to explain the asymptotic flatness of galaxy rotation curves, without the necessity of postulating the existence of “dark matter”. Milgrom showed that a number of other, novel predictions follow from his three postulates, and proposed these predictions as tests of the theory. Milgrom also proposed a set of guiding principles for how his nascent theory should be developed toward a more complete theory of gravity and cosmology.