The success of high-level programming models in Wireless Sensor Networks (WSNs) is heavily dependent on factors such as ease of programming, code well-structuring, degree of code reusability, and required software development effort. Component-based programming has been recognized as an effective approach to meet such requirements. Most of componentization efforts inWSNs were ineffective due to various reasons, such as high resource demand or limited scope of use. In this paper, we present REMORA, a new approach to practical and efficient component-based programming in WSNs. REMORA offers a well-structured programming paradigm that fits very well with resource limitations of embedded systems, including WSNs. Furthermore, the special attention to event handling in REMORA makes our proposal more practical for WSN applications, which are inherently event-driven. More importantly, the mutualism between REMORA and underlying system software promises a new direction towards separation of concerns in WSNs. Our evaluation results show that a well-configured REMORA application has an acceptable memory overhead and a negligible CPU cost.