Decentralized physical infrastructure network (DePIN) is currently one of the hottest narratives in Web3. In this paper, we present a new thesis of DePIN, namely the modular DePIN infrastructure. By retrospecting the evolution of software development platforms for building physical infrastructure networks, we describe the new technology trend of building DePIN applications on top of a community-owned modular DePIN infrastructure and highlight the characteristics of this new DePIN thesis from both technical and economic perspectives. In particular, the emerging modular DePIN infrastructure brings a number of research challenges that need to be further addressed through collaboration between academia and industry.