Explore the intricacies of Heavy Quark Effective Theory (HQET) and Soft-Collinear Effective Theory (SCET) in this advanced lecture, part of the School for Advanced Topics in Particle Physics (SATPP) series on Selected Topics in Effective Field Theories. Delve into these powerful theoretical frameworks used to describe heavy quark systems and high-energy processes involving light-like particles. Gain insights from expert physicist Matthias Neubert as he discusses the applications and implications of HQET and SCET in particle physics research. Designed for postdoctoral fellows and advanced PhD students in theoretical particle physics, this 1-hour 18-minute lecture offers a deep dive into essential technical tools for critically analyzing and constructively approaching complex phenomena in high-energy physics.