New Horizons in Ab Initio Theory of Atomic Nuclei Atomic nuclei are intriguing finite many-body quantum systems governed by the very complex residual strong force. Ab initio nuclear theory seeks to provide accurate predictions of nuclear properties and reaction processes starting from quarks/gluon considerations. I will discuss an innovative method that improves the predictive power of the ab initio framework and extends its reach towards currently inaccessible medium-mass nuclei.