Heavy flavor physics entered a new era when the Belle II experiment observed its first collision. There are several hints found so far by BaBar, Belle, and LHCb in particular, that suggest the physics beyond the Standard Model appearing in the loop processes at short distances. They will be further tested by higher precision experiments in the coming years, while the role of lattice QCD is to understand the long-distance physics quantitatively so that one can unambiguously isolate the short-distance physics from the experimental data. I summarize the status towards this goal and then look at the challenges we are facing.