This book reveals attention as the fundamental bottleneck constraining both human cognition and AI systems, drawing striking parallels between biological limits like working memory and computational challenges in transformers. Readers gain a unified framework to understand why attention is scarce across silicon and carbon, equipping technologists, researchers, and general readers with insights to design better AI, reclaim personal focus, and navigate the attention economy. Discover practical solutions from cross-disciplinary research that reframe human-AI relations as a shared challenge rather than competition.