The paper presents a theoretical framework for understanding the evolution of industrial districts from Marshall’s conceptualisation to today’s realities and theorisations of the industrial district as model of industrial organization and development. We discuss three generation of industrial districts: the first generations of districts were the seedbeds for the first industrial revolution. The second generations corresponded to the re-emergence of industrial districts in advanced and industrialised countries during the second half of the twentieth century, after the golden age of mass production. The current and third generation is being revealed resorting to scholarly observation. We will argue that each generation of industrial districts have emerged and grown in correspondence with specific technological, institutional and market conditions. Some evidence from the Italian case is presented.