The paper argues that a new category of infrastructures is emerging, user-driven, selforganizing and with de-centralized control: Inverse Infrastructures (IIs). IIs are not wellunderstood. Moreover, they represent a paradigm shift in infrastructure development. Their bottom-up development shows tension with the current socio-institutional framework for infrastructures. Internationally infrastructure laws and policies are based on a top-down and centralized view of infrastructures. Regulation is based on a control paradigm that does not fit the characteristics of inverse infrastructures and has no ways to deal with them. Policy (re)design is needed in the face of inverse infrastructure emergence. The paper analyses how these self-organizing infrastructures emerge and develop by focusing on coordination issues. Coordination is central to self-organization. Two clusters of II cases are analyzed on what triggers coordination and how subsequent coordination takes place (coordination mechanisms). Theoretical concepts are drawn from standardization theory, from studies on Open Source Software communities, and from theories of self-organizing systems (i.e. Complex Adaptive Systems and System-of-Systems theory). The two clusters of II cases are peer-to-peer networks (e.g. Napster, Gnutella and Joost) and wireless networks (Wireless Leiden and FON). The paper concludes that, similar to the behavior of ant colonies, II emergence can be understood as an accumulation of local attempts to optimize a situation. Complex citizen and citizen-company partnerships evolve which compete with existing infrastructure provisions and touch on public values (e.g. privacy, copyright). A policy response is needed. here is a widespread fascination among researchers of various disciplines