Abstract: A major goal of nuclear theory is to explain the wealth of data exhibited by nuclear systems in a fully microscopic approach.  In such an approach, which we refer to as the basic model of nuclear theory, the nucleons interact with each other via two and many-body effective interactions, and with external electroweak probes via effective current operators.  These effective interactions and currents are the main inputs to ab-initio methods that are aimed at solving the many-body Schrödinger equation associated with the nuclear system under consideration.  In this talk, I will review recent progress in Quantum Monte Carlo calculations of low-lying spectra, electroweak properties of light nuclei, and nucleonic matter equation of state.  Emphasis will be placed on calculations based on chiral effective field theory.