The Standard Model of particle physics can only be an effective theory of a more complete theory. The quest for this more complete theory is one of the most urgent open questions of modern particle physics. One experimental approach to solve this questions uses precision measurements of B-meson decays and their comparison to theoretical predictions. In this lecture this approach will be presented and measurements at the Belle and LHCb experiments will be discussed. 

• the CKM matrix
• the discovery of the b-quark
• B meson mixing
• CP violation in the B-system
• rare B decays