The Wireless Sensor Network (WSN) based IoT is an intelligent revolutionary system that benefits across various real-time applications. The advantages of WSN are employed for smart monitoring and the design of automated systems. In WSN based IoT, different types of sensors are placed in a distributed manner to perform the monitoring and controlling operations of smart IoT. Sensing plays a prominent role in IoT, and the accuracy of sensors is essential in such environments.
   The major applications of WSN based IoT are intelligent transportation systems, smart buildings, smart health care, smart surveillance, supply chains, and education. The intelligent transportation system accomplishes efficient road safety and increases road user comfort by predicting roadside hazards in advance using WSN. In smart home building, the WSN with IoT connects the physical and virtual world efficiently. In smart healthcare, the conditions of patients are frequently monitored through wearable sensors, and the reports are used to take timely actions.
   The WSN based IoT faces the novel applications requirements of humans by integrating smart wireless technologies. The grand challenges of WSN based IoT systems are scalability, security, privacy, resource efficiency, limited bandwidth, restricted energy, and self-automation.