Wireless Sensor Network Architecture: Wireless sensor networks continuously lead to the development of intelligent environments that are the next step in homes, buildings, transportation, etc. Like any other sensory organism, intelligent environments also depend on the sensory organism data to be captured from the real world. The sensors can be extroreceptors or proprioreceptors that work in, on or around the desired subject. Various challenges are faced by such networks ranging from sensing the required quantities to monitoring and collecting data, then evaluating the data to formulate meaningful decisions and necessary alarm functions as and when required. The complexity of wireless sensor networks continues to increase due to the plethora of available resources and technologies making it even more difficult to select components and therefore build a more robust, energy efficient and easy to use design. Hence the study of WSNs becomes more challenging as it includes huge amounts of knowledge from all disciplines. In this chapter we will briefly review the WSN architecture by outlining different communication networks and protocols, various physical sensors, signal processing and decision making, and some facts about home automation. Communication Networks and Protocols: A communication network will consist of nodes capable of transmit and receive messages over communication lines which may be wired or wireless. The most commonly used network topologies are mesh, star, ring, tree etc. A single network can contain one or more interconnected topologies. Networks can also be classified, depending on their area, into LAN (Local Area Network), MAN (Metropolitan Area Network) and WAN (...... half of the document ...... but one of the main causes of concern for the development of ad hoc networks Small MEMS sensors (electromechanical micro systems) are currently being developed which require much less energy and are made up of RF components such as capacitors, inductors, etc. They are manufactured in such a way as to use energies such as solar energy and vibrations. energy to further reduce energy consumption. Passive tags do not require any on-board power source and RFID tags are used which are very economical in applications such as automotive toll collection can also be done with the help of the software by programming sleep mode The distance between the source and the destination can be reduced and the signal can be optimized by placing repeaters as the power consumption increases by the square of the difference in the distance between the source and the destination..