Explore the foundations of Heavy Quark Effective Theory (HQET) and Soft-Collinear Effective Theory (SCET) in this comprehensive lecture by Matthias Neubert. Delve into the fundamental principles and applications of these powerful effective field theories in particle physics. Gain insights into how HQET and SCET provide systematic frameworks for describing heavy quark systems and high-energy processes involving collinear particles. Learn about the theoretical foundations, key concepts, and practical applications of these theories in understanding and calculating observables in particle physics. Suitable for postdoctoral fellows and advanced PhD students with a strong background in quantum field theory and the Standard Model of particle physics.