Describes how scientists are re-ordering knowledge to emphasize growth, change, and contingency Marks the broad contours of an ongoing revolution in scientific explanation While for much of the twentieth century scientists sought to explain objects and processes by reducing them to their component parts - nuclei into protons and neutrons, proteins into amino acids, and so on - over the past forty years there has been a marked turn toward explaining phenomena by building them up rather than breaking them down. This collection reflects on the history and significance of this turn toward "growing explanations" from the bottom up. The essays show how this strategy - based on a widespread appreciation for complexity even in apparently simple processes and on the capacity of computers to simulate such complexity - has played out in a broad array of sciences. They describe how scientists are re-ordering knowledge to emphasize growth, change, and contingency and, in so doing, are revealing even phenomena long considered elementary - like particles and genes - as emergent properties of dynamic processes.