For about 80 years, physicists have worked on understanding the atomic nucleus in fundamental terms, but only the past decade has brought about a dramatic breakthrough towards achieving this goal. The fundamental (“microscopic”, “ab initio”) approach has two ingredients: the basic forces between nucleons and quantum many-body theory. Since the nuclear force is a manifestation of strong interactions, any serious derivation has to start from quantum chromodynamics (QCD). However, QCD is non-perturbative at low energies, which renders its application to nuclear physics exceedingly difficult. About two decades ago, it was shown successfully that the way out of this dilemma is an effective field theory that observes the same symmetries as low-energy QCD. In parallel with these advances, there has been significant progress in the treatment of the quantum many-body problem. The improvement of algorithms and the dramatic increase in computing power have made it possible to obtain essentially exact solutions of systems with up to about 40 nucleons. These achievements have allowed for a deeper understanding of nuclear two- and many-body forces, the exact structure of light nuclei (including so-called “exotic” nuclei), and nuclear reactions. The outcome of this research has widespread impact on society, ranging from nuclear medicine to nuclear energy and everything in-between.