Recently, an attempt to integrate sensors and networks in a high-order dimension has been carried out. Various concepts for this integration have been proposed thus far; for example, sensor networks, ubiquitous sensor networks, ambient sensor networks, Internet of Things (IoT), and Trillion Sensors Universe, which are almost the same concepts in terms of the integration of sensors and networks. Behind the rapid expansion of these concepts are the rapid improvement of the performance of micro-electromechanical system (MEMS) sensors, reductions in their size and fabrication cost, and the realization of their mass production, as well as the establishment of network technology, the advancement of processors and wireless devices, and the realization of small highcapacity power sources. In this perspective series, I will explain the integration of sensors and networks in several sessions. The planned contents include the history of the sophistication of sensors, the outline of sensor networks, fundamental technologies for supporting mass production, the integration of different types of sensor, sensor interfaces, peripheral technologies for connecting networks, stand-alone power sources, and examples and future prospects of sensor networks. In this session, I will describe the history of the sophistication of sensors and the outline of sensor networks.