The use of optical wireless technologies for wireless signal transmissions has a long history, and a brief snapshot of optical wireless communication (OWC) systems is illustrated. The OWC principle uses modulated optical signal, which propagates through the free space to the receiver side, to provide data transmissions. In addition to wireless personal and local area network's, the OWC principle is also widely used in the wireless body area network, such as the transmission of information collected by bio-sensors inside or on the human body to nearby communication terminals. The directional propagation property of light and the practically unlimited bandwidth available in the optical spectrum are other key reasons of using OWC in space communications. Compared to traditional applications in outdoor and relatively long-range scenarios, the renewed interest in OWC principle focuses more on the short-range and indoor environments. The chapter also presents an overview of the key concepts discussed in this book.