This book explores how a long-term innovation can take place based on historical analyses of the development of reverse osmosis (RO) membrane from the early 1950s to the mid-2010s. The RO membrane is a critical material for desalination that is a key to solve water shortages becoming serious in many places of the world.The authors conducted in-depth field studies as well as analyses of rich archival data to demonstrate how researchers, engineers, managers, entrepreneurs, and policymakers interacted each other for this material innovation to be realized. A series of historical analyses in this book uncovered that initial government supports, strategic niche markets, emergence of breakthrough technology, and company-specific rationales played significant roles for companies to overcome four types of uncertainty, technological, market, competition, and social/organizational ones, and enabled the companies to persistently invest in the development and commercialization of the RO membrane.This book depicts that innovation does not arise on a sudden, but that it is actualized through long lasting process with turns and twists, which is driven by many non-economic rationales beyond economic motives.