In this chapter, the authors briefly outline the emergence of world-systems approaches first formulated by Immanuel Wallerstein and expanded by Janet Abu-Lughod. They discuss the emergence of connectivities as well as hierarchies over the centuries in global perspective. Conquest and colonization increased inequalities between peoples in macro-regions and long-distance trade often turned into plunder. The racialization of labour forces beginning with slavery involved an ideology of skin colour-coding that underpinned the politico-economic power of European-Atlantic and, subsequently, North Atlantic states. Skin-colour hierarchies have also been developed in other segments of the world. In this frame, migrants, despite being integral and irreplaceable parts of global labour markets, are often excluded from social and political rights in the societies to which they contribute their labour. The authors rely on World Bank data to discuss global migrations due to global inequalities.