In this book, we will give an overview of what is known about the relationships between the design and structure of health systems, health service provision and utilisation, and inequalities in population health. This will show the added value of combining health systems, health services, and population health research; areas that have become siloed. In doing so, we hope to create awareness among researchers to look beyond the boundaries of their own research field and promote multidisciplinary collaboration. This first chapter introduces the three fields of health systems research, health services research, and population health research and their role in understanding factors creating health inequalities and measures to mitigate them. We briefly introduce these three areas of research (Sects. 1.2–1.4). They have overlaps (Sect. 1.5) but tend to become siloed because they are seen as separate academic specialisations. We end this chapter by outlining our approach and the aims of the whole book (Sect. 1.6) together with some conclusions (Sect. 1.7).