The seminar offers a comprehensive understanding of in-work poverty in Europe. Working poor are individuals who are gainfully employed, but their salary or their household income is below the poverty threshold. Therefore, in-work poverty arises at intersection of labor market and poverty dynamics: on the one hand, individual resources are related to the likelihood of experiencing unfavourable labor market arrangements leading to poverty (e.g. low-wage or temporary contracts); on the other hand, specific family structure or family-life-course transitions are associated with different levels of households’ economic wellbeing. The seminar will examine how in-work poverty became a critical issue in the US first, and in Europe later. We will then discuss the theoretical and methodological challenges of defining and measuring in-work poverty. The prevalence of working poor over time and for specific social groups will be considered across welfare and labor market regimes. In a life-course perspective, special attention will be devoted to the generational and gender cleavages. Finally, implications for policies against in-work poverty will be discussed in light of both individual and household definitions.