Buck discusses the science of habit formation, specifically focusing on exercise. He explains the habit loop, which consists of a cue, routine, and payoff, and how habits are engineered through repetition and reward. Buck emphasizes the role of dopamine in motivating and craving habits and highlights the importance of consistency and creating a consistent environment. He provides practical tips for creating the habit of exercise, such as starting small, stacking habits, making it fun, leveraging social support, setting goals, tracking progress, and preparing for setbacks.