Chapter 2 discusses the linkages between technology and environmental sustainability. It starts out with some brief context on key concepts in the contemporary debate: transitions, transformations, and resilience. The chapter continues with two concepts that are central for this book: the idea of the ‘techno-fix’, in the sense of technology potentially providing partial solutions for intractable social- and political problems; and the notion of lock-in, where past technological choices may be difficult to revise or reverse in the present. Further, it develops the notion of technological ‘promises’ and ‘perils’ as key elements of my theoretical framework: transformative novel technologies could produce substantial benefits but also give rise to various types of harm, providing a rationale for governance responses that capture the former and avoid the latter. At the same time, transformative novel technologies tend to be ambiguous as the precise extent to which they entail different types of promises and perils is usually unknown, uncertain or disputed.