Jonah Berger's book "Contagious: Why Things Catch On," explores the science behind virality in products, ideas, and behaviors. The book introduces six key principles—Social Currency, Triggers, Emotion, Public, Practical Value, and Stories (STEPPS)—that make things more likely to be talked about and shared. Through numerous examples ranging from a hundred-dollar cheesesteak to viral YouTube videos and social causes, the author illustrates how these principles influence human behavior and contribute to widespread adoption. The book emphasize the power of social influence and word-of-mouth marketing, both online and offline, as critical drivers of success, often more so than traditional advertising or inherent product quality.