This lecture discusses the process of polymer collapse, focusing on protein folding and interactions. The instructor explains how hydrophobicity and other interactions drive the collapse to a compact state, emphasizing the hierarchical nature of protein folding. The lecture also delves into the meaning of the B₂ factor and the role of attractive interactions in polymer collapse. Various concepts such as the Flory approach, relevant interactions, and the impact of temperature on collapse are explored. The discussion extends to the necessity of monomers to avoid each other and the implications of attractive potentials in DNA-binding proteins.