Extending first principles of nuclear structure to all open-shell nuclei: The breadth of first-principles nuclear structure calculations in medium- and heavy-mass nuclei has largely been limited to closed-shell and neighboring nuclei or spherical even-even systems. As reported in Physical Review Letters (2017), TRIUMF nuclear theorists developed a new approach for calculating virtually any property of the atomic nucleus. It generalizes the ideas of the nuclear shell model to capture the effects of three-nucleon forces among valence nucleons with a valence-space Hamiltonian specifically targeted to each nucleus of interest. Predicted ground-state energies from carbon through nickel agree with results of other large-space ab initio methods, generally to the 1% level. This approach then effectively extends the reach of ab initio nuclear structure calculations to essentially all medium- and many heavy-mass nuclei.