From the endosymbiosis of single-celled organisms 3.5 billion years ago to today's globalized supply chain networks, dependency has been a core code running through the evolution of life and human civilization. It's not a sign of weakness, but rather the wisdom of survival and development—the energy symbiosis between mitochondria and cells supports the birth of complex life, the food chain in ecosystems maintains natural balance, and the division of labor and cooperation in human society has created the miracle of civilization. However, dependency also carries hidden risks: overdependence can lead to vulnerability, and power imbalances can lead to control and oppression. This book systematically analyzes the evolution of dependency relationships, from the microscopic mechanisms of the origins of life to the macroscopic operations of social networks, revealing its dual nature and resilience, helping us maintain autonomy in connection and build a healthy balance in dependency.