MCMH has been generally underestimated in urban and architectural studies, and there is still a lack of comparative analysis and global perspectives. From 2019 to today, the COST Action Middle-Class Mass Housing in Europe (MCMH-EU) has created a transnational network among researchers conducting studies on MCMH sites in Europe since the 1950s. The Action aims to develop a more comprehensive understanding of MCMH sprawl in cities and deepen the knowledge by focusing on the existing cases, public policies, new concepts and research methodologies. Besides the current methods, surveys, and contextualisation that allow us to map the existing cases, the Action also aims to show the diversity and resilience of MCMH in terms of adapting to the current urban and social conditions.