This lecture discusses CP violation in the early universe, focusing on the matter/antimatter asymmetry. It covers the conditions required for generating this asymmetry, the role of CP violation in particle physics, and the CKM matrix. The GIM mechanism and weak interaction of quarks are explained, along with Feynman rules and the CPLEAR experiment. The lecture also delves into strangeness oscillations, neutral kaon decays, and CP violation in the kaon system. It concludes with a summary of the CKM matrix, CP violation in quark interactions, and the need for additional mechanisms to explain matter-antimatter asymmetry.