Reactor neutrinos have been an important tool for both discovery and precision measurement in the history of neutrino studies. Since the first generation of reactor neutrino experiments in the 1950s, the detector technology has advanced greatly. New ideas, new knowledge, and modern software have also enhanced the power of the experiments. The current reactor neutrino experiments, Daya Bay, Double Chooz, and RENO, have led neutrino physics into the precision era. In this article, we review these developments and advances, address the key issues in designing a state-of-the-art reactor neutrino experiment, and explain how the challenging requirements of determining the neutrino mass hierarchy with the next-generation experiment JUNO could be realized in the near future.