The calculation of $\epsilon'$ within the Standard Model has been a critical goal of particle physics since its definitive measurement sixteen years ago. The small size of this quantity makes it extremely sensitive to new Beyond the Standard Model sources of CP violation that may help to explain the origin of the matter/antimatter asymmetry in the Universe. Given the highly non-perturbative character of this quantity, lattice QCD is the favored approach. After more than six years of development, a successful lattice approach has emerged based on the Lellouch-L\"uscher finite volume relation and G-parity boundary conditions. We discuss our first complete, realistic calculation of $\epsilon'$, published in PRL one year ago.