Explore the second lecture on the inflationary paradigm in cosmology, delivered by William Kinney as part of the Physics of the Early Universe program. Delve into key concepts such as scalar fields, stress energy, slow roll inflation, and quantum fluctuations. Examine worked examples of chaotic inflation and learn about metric perturbations, curvature perturbations, and scalar field perturbations. Gain insights into quantization, mode normalization, and the power spectrum in de Sitter space. Conclude with discussions on tensor modes and the consistency relation, followed by a Q&A session. This comprehensive lecture provides a deep dive into the mathematical and theoretical foundations of inflationary cosmology for graduate students and postdoctoral fellows.