The aim of this chapter is to investigate critical aspects for the quality of Swedish preschool. High-quality preschools promote equality and equity, lead to short and long-term benefits for children’s health, wellbeing, lifelong learning and development, as well as benefits for society. Early intervention, through high-quality preschool, is therefore important to make the necessary changes in children’s lives to allow positive life trajectories. In three studies, the quality of the participating preschools was analysed from Bronfenbrenner’s ecological system theory and an intersubjective perspective on quality, in the light of research on preschool quality and related to the goals and intentions of the Swedish preschool curriculum. The knowledge gained by these studies highlights a gap between children and teachers’ perspectives and between policy intentions and the preschool practice. Over time, the results indicate a decrease in quality in certain areas and an enhancement in others. Together, the results from these studies describe and highlight critical aspects for the quality that are of interest in a policy perspective, for the profession and for the field of early childhood research.