In this paper, we advocate asymmetric function placement as one of guiding principles to architect sensor network systems. We demonstrate its generic applicability and effectiveness by applying this principle to three typical sensor network technologies, namely, localization (Spotlight), sensing (uSense) and communication (mNets). These technologies have very dissimilar features, representing a wide spectrum of system design requirements. We have invested significant effort to design, implement and evaluate our techniques on TinyOS/Mote testbeds. The results from several running systems indicate that asymmetric function placement is a powerful guiding principle to achieve efficiency and high-performance simultaneously in wireless sensor networks. At the end, we exam the system features that discourage the use of asymmetric function placement and approaches to address them.