In the previous sessions, the advancement of sensor devices and their technologies was briefly outlined. In this session, I discuss how such sensors are used and incorporated into network systems. One pioneering commercial network system is the DECnet, which was proposed and implemented by the Digital Equipment Corporation (also known as DEC) in the 1970s. In parallel, the Advanced Research Projects Agency Network (ARPANET) project was an attempt to combine numerous computers over a wide area, leading to the launch of the email and bulletin board systems in the 1980s and the World Wide Web system in the 1990s. Owing to the progress in the development of hardware for wireless networks, high-speed low-cost wireless network modules have become easily available since 2000. Currently, networks extend all over the world and laptop PCs, mobile terminals, and sensor systems can be easily and wirelessly connected to the networks.