Sustainability transitions research explores how societies transform socio-technical systems towards evolving sustainability goals. This chapter introduces key concepts, development, and significance of this interdisciplinary field. We define sustainability transitions through three core components: socio-technical systems combining technology and social structures, transition processes as multi-dimensional shifts over long timespans, and the evolving, contested nature of sustainability goals. Since its 1990s origins, the field has expanded to include diverse theoretical frameworks and methods. While established frameworks offer valuable tools, emerging research on spatial dimensions, power dynamics, and methodological diversification is crucial for addressing contemporary challenges. This chapter lays the foundation for the handbook, previewing key debates and themes explored in subsequent chapters on theoretical frameworks, transition dynamics, methodologies, and future research directions.

Analysing interactions between niches and regimes is critically important for understanding sustainability transitions. What complicates interaction is the fact that sustainability is often understood and pursued differently in regimes compared to niches. That means the aims and criteria for innovation can be different on either side of the interaction. A paradox arises in which interaction will be easiest when there is already good alignment between niche and regime sustainability criteria, but such alignment will by definition not demand very great changes in the regime nor empower more radical niche experiments. In practice, four different interactions coexist: differentiation; co-option; hybridisation; and criticism. These interactions work in both directions, can be interdependent upon one another, and influence wider change processes over time. It becomes problematic to conceive reconfiguration as a single transition process originating in niches and linking to regimes. This is illustrated with an example that contrasts sustainability in the automation regime of the Fourth Industrial Revolution (4IR) with a niche space that we call post-automation. In becoming attentive to niche-regime interactions, so the politics of sustainable transitions becomes clearer.

While most sustainability transitions researchers agree on the need for cross-disciplinary collaboration, such collaborations can be difficult in practice. Scholars often disagree on (a) how to understand the world (ontology) and (b) what constitutes important knowledge about transitions (epistemology). From this observation, this chapter explores ontological and epistemological debates in sustainability transitions research. It begins by outlining dominant frameworks, particularly the multi-level perspective (MLP), and their foundational assumptions drawn from evolutionary economics and science and technology studies (STS). The chapter identifies two main criticisms of the MLP: the need for an expanded epistemic focus and ontological critiques from proponents of ‘flat ontologies’ and critical realists. It then discusses new epistemological approaches that challenge the dominant narrative that transitions primarily emerge through innovation journeys. These criticisms focus on capitalism, coloniality, and justice, highlighting how mainstream transition studies tend to externalise such concerns. The chapter concludes by supporting radical theoretical pluralism as key to understanding sustainability transitions’ increasing complexities.

Social practice theories have become increasingly prominent in sustainability transitions research. By drawing attention to everyday life and social dynamics as key issues in sustainability transitions alongside technologies, infrastructures, and policies, practice theories provide valuable contributions to transition research, governance, and intervention design. Instead of focusing solely on individual behaviours or structures, they view practices - collective patterns of human activity - as the central unit of analysis, emerging from and at the same time shaping (infra)structures and behaviours. Therefore, practice theories can be fruitfully utilised as an alternative or complementary perspective on sustainability transition frameworks to identify, explain and address the social dynamics of change. In this chapter, we show how social practice theories can be used to study - as well as to bring about - innovations and disruptions for sustainability transitions. We start by providing a concise overview of what practices are and how they change. We also showcase an example of a practice theory-inspired change initiative as well as discuss the main differences, similarities, and synergies of social practice theories and the multi-level perspective of socio-technical transitions. We end with outlining some of the on-going debates and further research needs.

This chapter discusses the role of visions, expectations, and socio-technical imaginaries in shaping sustainability transitions. Imagining futures different from current socio-technical regimes is essential for legitimizing and mobilizing niche technologies and driving system change. More recently, mission-oriented and transformative innovation policies have emphasised envisioning and collective expectations in defining and implementing long-term goals. The chapter introduces the historical development of these concepts within sustainability transition studies, including transition management, strategic niche management, and technological innovation systems. It presents and compares various anticipatory practices and techniques for exploring and shaping transition dynamics. ‘Futuring methods’ such as scenario development, technology foresight, roadmapping, and modelling are not just neutral tools but shape political problems and solutions. The chapter concludes by illustrating the influence of visions, expectations, and imaginaries in the historical evolution of hydrogen futures and highlighting key research trends.

Sustainability transitions involve complex, long-term societal changes shaped by diverse actors within dynamic structural contexts. This chapter takes a role based perspective, distinguishing between social roles, which evolve with societal values and priorities, and transition roles, which reflect actors’ engagement with transition dynamics. It explores conceptual and empirical applications, highlighting research trends and gaps. Social roles provide insights into institutional change over time, while transition roles reveal how actors strategically position themselves within transitions. Emphasizing the fluid and negotiated nature of roles, the chapter concludes by advocating for longitudinal studies on social roles and the use of transition roles as a boundary object for action-oriented, transdisciplinary sustainability research.

Sustainability transitions have often been described as involving ‘disruptions’. However, many writings in this field have been imprecise about what disruption means in the context of transitions, beyond the disruption of the status quo. References to disruptions in the literature have ranged from a discourse on disruptive niche innovations to disruptive landscape influences. A systematic literature review revealed that the conceptualisation of disruption was often imprecise and empirical studies were largely focused on the energy sector. In this chapter, we build on this definition of disruption and complement the understanding by reviewing the most recent literature, adding to the initial review. This chapter provides much-needed clarity on the conceptual confusion that has emerged and evaluates the links between the concept of disruption and the ways in which mainstream technologies, practices, and business models in socio-technical regimes need to be phased out, destabilised, or undergo decline. We conclude by examining the relevance of the concept of disruption to emerging scholarly and societal debates on just transitions.

Transitions research has gained traction in sustainability studies for its systemic approach to environmental challenges. A central tenet is that the persistence of these challenges can be attributed to ‘system failures’, and that system innovation is needed, i.e. a multitude of innovations that co-evolve into system-wide transformations. However, many contrasting views of ‘systems’ and ‘systemic frameworks’ are seemingly always clamouring for attention, whilst it is not always clear what they’re referring to. Taking a reflexive methodology approach, this chapter addresses recurring questions: Transforming ‘systems’: Which? How? Whose? Why? Whither? Whence? For instance, is transitioning the ‘mobility system’ a matter of electrification or of unlearning car dependency? In transitioning the ‘energy system’, is importation of rare minerals a central part or an externality? The chapter presents a methodological overview of systems analysis in transitions research. It brings out how transitions research has developed a fine sense of Critical Systems Thinking. On the other hand, it also shows the need for further methodological reflection on the study of transitioning ‘systems’.

In the past decade, the geographical and conceptual breadth of sustainability transitions has expanded, especially in Asia, Africa and Latin America. Increasing attention is paid to social, economic and environmental issues in the ‘Global South’, where decades of colonial rule have shaped infrastructures and institutions. In recent years, the literature has taken a ‘decolonial turn’, underlining the risks of reproducing colonial ways of control, power, privilege, domination, and disassociation with Nature. This chapter reviews this emerging literature, articulating why and how contexts differ between Global South and North and how sustainability transitions theories could be more meaningful in Global South contexts. The central research question is: how could we analyse and enact sustainability transitions in the Global South in a way that transcends historical challenges of colonial modernity and undesired development while pursuing just futures? The review is organised around five themes: niches, regimes, change, justice, and knowledge diversity. The chapter proposes ways to go deeper into these themes in setting a research agenda for future sustainability transitions in the Global South.

Although it is well-known that major technological change can impact multiple socio-technical systems and their patterns of interaction, the issue of multi system dynamics in transitions has until recently not attracted much attention. For new sustainability transition phenomena such as decarbonisation efforts across various systems or circular economy initiatives that involve entire value chains, it is vital to better understand the ways, in which multiple systems interact and shape each other’s transitions. The goal of this chapter is to provide overview and orientation for a rapidly emerging topic by taking stock of the current state of knowledge. We review contributions from three main conceptual frameworks in transition studies: the technological innovation systems approach, the multi-level perspective, and deep transitions. On that basis, we discuss similarities, differences, and open issues to identify a future research agenda for the emerging area of multi-system dynamics in transitions.

In today’s world of increasing spatial inequalities, geopolitical tensions and global shifts in value chains, having a solid grasp of the spatial and multi-scalar dynamics that condition transition dynamics is of ever more importance. Initial theories of sustainability transitions have been criticised for being insufficiently equipped to assess the benefits, conflicts and unevenness that are constituted by the territorial contexts in which transitions dynamics and pathways unfold. Questions how sustainability transitions emerge across places and scales were largely off the radar. Interest and engagement with geographical dimensions of sustainability transitions grew however quickly into a prominent sub-field, characterised by a fruitful trading zone populated by geographers, transition scholars and other social scientists seeking to better account for place specificity, multi-scalarity, and spatial unevenness. This chapter outlines the contours of the Geography of Sustainability Transitions (GeoST) wider theoretical research agenda and ongoing debates, framing these specifically around conceptualisations of place and scale.

This chapter argues that reflexivity - an introspective process in which researchers turn their engagement into an object of research - is essential to sustainability transitions research (STR). Reflexivity in STR encompasses not only the non-neutrality of its normative categories, such as ‘sustainability’ and ‘radical’, but also its descriptive categories, including ‘regime’ and ‘system’. This inherent social embeddedness, or ‘engagedness’, positions transition researchers with both an inescapable responsibility and a unique opportunity to shape their engagement reflexively. Reflexivity, which is relevant at every stage of STR, is illustrated in terms of research orientation, role and positionality. It highlights that much of reflexivity lies in the question of how - and with what kind of awareness - you are personally doing what you are doing. As a transition researcher, you are in a comparatively powerful societal position. Your choices matter and make a difference in the world.

Innovation systems take a holistic view of the dynamics shaping innovation, emphasizing actors, institutions, and networks as key structural elements. These interact to create positive or negative feedback loops. Initially, innovation systems focused on national competitiveness and were technology-neutral. The introduction of technological innovation systems (TIS), the focus of this chapter, shifted attention to the emergence of specific technologies, particularly sustainable ones that face market barriers. This made TIS a foundational framework in sustainability transitions research. The introduction of TIS ‘functions’ marked a key milestone in the field. Over time, TIS has evolved, addressing context, geography, and system interactions. Scholars continue to expand innovation system frameworks, exploring missions, life cycles, and destabilisation. This work increasingly integrates both technological and social innovation, supporting pathways towards sustainability.

Pressing environmental and societal challenges, such as the climate crisis and social inequality, demand policy interventions to steer and accelerate sustainability transitions. This chapter highlights four key intervention areas: providing direction to transitions (directionality), fostering innovation (niche support), phasing out unsustainable practices (regime destabilisation), and coordinating transition processes (coordination). We outline their theoretical rationale in transition studies and offer interdisciplinary insights from policy research. Based on a comprehensive literature review, we present 15 concrete policy interventions to transform production and consumption systems. Evaluating these interventions with empirical findings from leading transition journals, we highlight research opportunities at the intersection of public policy and sustainability transitions. Given the resistance and contestation around transformational policies, we aim to foster interdisciplinary exchange on how to accelerate sustainability transitions.

Sustainability transitions can be understood as the transformation of socio-technical systems towards the sustainable provision of societal functions. Socio-technical systems are held together by formal and informal rules, also called institutions. For sustainability transitions to materialise, the formal and informal rules of socio-technical systems need to change. Institutional change is often driven by coordinated collective efforts - typically in the form of coalitions - that mobilise actors, shape policies, and influence socio-technical environments to favour sustainable innovations. The chapter defines coalitions and related concepts such as alliances, social movements, and networks, and reviews their roles within established sustainability transition frameworks, including the multi-level perspective, technological innovation systems, strategic niche management, and transition management. The chapter also introduces theoretical strands that use different types of coalition concepts and discusses how they can be applied to sustainability transitions, and finally highlights valuable avenues for future coalition-related research in the field of sustainability transition studies.