Wireless sensor networks (WSN), which are integrated with sensors, wireless communications, and embedded systems, have attracted intense attention from both academic and industrial fields. Through the interconnections among different nodes in WSN systems, the aim of ubiquitous intelligence could be achieved. In this paper, we present an overview concerning the recent development of wireless sensor networks. The topics related to WSN designing issues are investigated first, and then the device components and networks structures of WSN are explored. In addition, several cases for WSN-enabled applications are briefly introduced to provide a more comprehensive viewpoint for the development of WSN systems.