Terahertz (THz) communications is seen as a transmission technology to achieve wireless transmission data rates of several 10 s of Gbps up 1 Tbps. One drawback of transmission at carrier frequencies in the THz range are high path losses, which are much higher compared to that at lower carrier frequencies. This has consequences on the design of THz communication systems, which cannot be designed and characterised as a scaled and incremental version of a lower-frequency system. This is accompanied by the need for a paradigm shift for measurement procedures in predicting the performance of THz communication systems in real environments. The capability to perform measurements and the development of metrological concepts to evaluate these measurements in a well-defined way are crucial for the advance of THz communication systems. This chapter introduces the motivation for starting the project DFG FOR 2863 Meteracom (Metrology for THz Communications), describes the structure of the project, and provides the outline of this book, which is meant to summarise the main results.