Teamwork in software engineering is time-consuming and problematic. In this paper, we explore how to better support developers' collaboration in teamwork, focusing on the software implementation phase happening in the integrated development environment (IDE). Conducting a qualitative investigation, we learn that developers' teamwork needs mostly regard coordination, rather than concurrent work on the same (sub)task, and that developers successfully deal with scenarios considered problematic in literature, but they have problems dealing with breaking changes made by peers on the same project. We derive implications and recommendations. Based on one of the latter, we analyze the current IDE support for receiving code changes, finding that historical information is neither visible nor easily accessible. Consequently, we devise and qualitatively evaluate BELLEVUE, the design of an IDE extension to make received changes always visible and code history accessible in the editor.@en