This deliverable provides conceptual background for the FITTER understanding of just transition processes and contributes to existing knowledge by critically assessing mainstream approaches to the twin transition. The aim is to broaden our understanding of the relationship between the twin transition and existing structural inequalities through the problematization of how the economy, the labour market and inequalities themselves are defined in the European Union (EU) context, and through a holistic approach to policy making. This approach informs the development of the FITTER approach and FITTER methodology, providing critical lenses through which the other methodological steps of the research process will be examined.