The creation of techniques, languages and tools to support building software from modular parts has enabled the development and evolution of large complex software systems. For many years, the focus of modularity was on the structure of the software system. The thinking was that the right modularity would enable software teams involved in different pieces of the system to work as independently as possible. As a community, we learned over the years that a system has no one optimal modularity, and in fact, the work that is undertaken to add new features or fix defects often crosscuts the modularity of the software. The research we conducted on task contexts and Mylyn over fifteen years ago recognized that capturing the activity performed on development tasks provided a means to make explicit emergent modularity for a system. With Mylyn, we explored how the activity of one developer could enable the surfacing of emergent modularity to help a developer perform tasks on a software system. Through stewardship of the Mylyn open source project and the creation of Tasktop Technologies, we brought these ideas into use in industry. Over the past decade, through interactions with practicing developers and their organizations, we have learned more about how modularity emerges at the individual developer, team, and organizational levels. Tasktop’s products moved accordingly from supporting the activity of individual developers to supporting the streams of value teams within an organization produce. In this talk, we will discuss how following the flow of tasks within software development supports value stream management and outline open research questions about the socio-technical aspects of developing complex software systems.