<div> The recent development of easy-to-use sources and detectors of terahertz radiation has enabled growth in applications of terahertz (Thz) imaging and sensing. Terahertz radiation does not damage tissues and DNA, unlike X-rays, so it is a good candidate for medical imaging. Many materials of interest have unique spectral "fingerprints" in the Thz range and this makes terahertz technology attractive for scientific research, sensing and imaging. There are many possible uses of Thz sensing and imaging in manufacturing, quality control, and process monitoring. The editor and contributors review the fundamentals of Thz technology, explain the recent progress and techniques in this technology and finally explore the applications of terahertz technology.<BR> <br> Part one discusses the generation, detection and emission of waves, surface plasmon polaritons, terahertz near-field imaging and sensing, room temperature terahertz detectors and terahertz wireless communications. Part two discusses recent progress and such novel techniques in terahertz technology as terahertz bio-sensing, array imagers, and resonant field enhancement of terahertz waves. Finally, the conclusion explores applications of terahertz technology, including applications in tomographic imaging and material spectroscopy, art conservation, and the aerospace, wood products, semiconductor and pharmaceutical industries.</div>