Uncertainty can appear in all aspects of software development: uncertainty in requirements analysis, design decisions, implementation, and testing. As the research on uncertainty is so young, there are many issues to be tackled. Modularity for Uncertainty is one of them. If uncertainty can be dealt with modularly, we can add or delete uncertain concerns to/from models, code, and tests whenever these concerns arise or are fixed to certain concerns. To deal with this challenging issue, we propose a modularization mechanism for uncertainty. Agile methods embrace change to accept changeable user requirements. On the other hand, our approach embraces uncertainty to support exploratory development. This paper sets out a focused research agenda for uncertainty in terms of the new modularity vision.