Explore the evolution and challenges of estimating human motion in this comprehensive lecture by Michael Black. Delve into the historical context, key concepts, and technological advancements in the field of human motion estimation. Learn about various techniques such as relaxation labelling, kinematic trees, stochastic search, and graphical models. Discover the complexities of modeling the human body, including shape identity, scanning methods, and deformation processes. Gain insights into the development of virtual humans, the importance of body shape and pose estimation, and the application of these concepts in tracking infants and analyzing interpersonal interactions. Understand the progression from simple body models to more complex representations, and explore the potential future directions in this fascinating area of research.