Developing countries have for decades been trying to catch up with the industrialized high-income countries, but only a few have succeeded. Historically, structural transformation has been a powerful engine of growth and job creation. Traditional development aid is inadequate to address the bottlenecks for structural transformation, and is hence ineffective. In this book, Justin Yifu Lin and Yan Wang use the theoretical foundations of New Structural Economics to examine South-South development aid and cooperation from the angle of structural transformation. By studying the successful economic transformation of countries such as China and South Korea through 'multiple win' solutions based on comparative advantages and economy of scale, and by presenting new ideas and different perspectives from emerging market economies such as Brazil, India and other BRICS countries, they bring a new narrative to broaden the ongoing discussions of post-2015 development aid and cooperation as well as the definitions of aid and cooperation.