Gateways have long been perceived and designed for providing interoperability between heterogeneous systems. In computer communications and networking, gateways have been primarily designed to provide packet level translations and at times for compression. In wireless sensor networks, the role of gateways is also limited to the same. The book takes a boldly different perspective of the role of these gateways. It purports increased influence and overarching role of gateways. It brings about elevated participation of gateways in communication, routing and application-specific operations. Deployments of gateways for sensor grids is also analysed for performance. Case study of 6LoWPANs as a practical example of gateways is interspersed. Mathematical modelling, simulations and experimental evaluations are provided to substantiate the proposed role of gateways.