Wireless sensor networks are collections of highly distributed, small, and lightweight wireless sensor nodes that monitor the environment or systems through physical measurement. Once the Zigbee and the IEEE 802.11 standards are approved and embraced, wireless sensor nodes will be capable of supporting interoperability among a wide range of mobile and fixed devices from different manufacturers. This paper reviews some of the fundamental mechanisms of wireless sensor networks including their architecture, topology, data integration, routing techniques, and applications. Sensor network applications include both military and civilian monitoring in both rural and urban environments. Wireless sensor networks hold great potential for improving control, conservation, convenience, efficiency, reliability flexibility, and safety in network environments.