Each process of designing of visualization is an opportunity to learn new things about how visualizations and data impact people and the world we live in. In this talk, I’ll discuss a specific research-based approach to designing visualizations — design study — and present a variety of insights that have emerged within my research group when we conduct them. These insights range from the role of personal knowledge in data analysis to the need for collaborative systems that enable data-supported insights by more people. These insights point to the opportunity for critical approaches to radically change the ways we design visualizations for data analysis.