Rob DeLine, a Principal Researcher at Microsoft Research, has spent the last twenty-five years designing programming environments for a variety of audiences: end users making 3D environments (Alice); software architects composing systems (Unicon); professional programmers exploring unfamiliar code (Code Thumbnails, Code Canvas, Debugger Canvas); and, most recently, data scientists analyzing streaming data (Tempe). He is a strong advocate of user-centered design and founded a research group applying that approach to software development tools. This approach aims for a virtuous cycle: conducting empirical studies to understand software development practices; inventing technologies that aim to improve those practices; and then deploying these technologies to test whether they actually do.