An elegant, mind-bending introduction to Complexity Theory, the science of how complex systems behave-from cells to ecosystems to human beings-that illuminates the very nature of life itself. The great scientific revolutions of the early twentieth century-the Theory of Relativity and Quantum Mechanics-are well-known, but another theory of equal profundity was developed by mathematicians at the end of the last century: an outgrowth of Chaos Theory, Complexity Theory is the science of organic life. Complexity rises up out of randomness to bring life into our universe, from quantum foam to single-celled organisms, human beings to entire ecosystems and beyond. In this concise and elegant volume, physician, scientist, and philosopher Neil Theise demonstrates how atoms and molecules, bodies and planetary systems all combine self-organization and unpredictability to build something greater than the sum of their parts. Each chapter illuminates in clear and accessible prose the many surprising underlying connections within a universe that is itself one vast complex system-between ant colonies and economic bubbles, cancer and traffic patterns, murmurations of starlings and crowds walking down the street-explaining why infinitesimal patterns configure the world as we know it. Under Theise's microscope, readers are invited to explore topics from the permeable boundaries of our bodies to the very nature of consciousness itself, as he takes us to the frontiers of human knowledge, where science meets philosophy. Notes on Complexity shows us that as assumptions about our world are continually upended, learning the simple principles of Complexity can radically reframe our perceptions. Complexity has the power to restore wonder to our experience of the everyday, allowing us to approach the world with greater understanding and a renewed sense of meaning.