THz radiation, which involves a part of the electromagnetic spectrum situated between microwaves and infrared, has been attracting more and more attention of researchers working in many areas of basic and applied sciences. To name a few, one can mention, e.g., quantum optics, solid state physics, technology of metamaterials, fast communication or medicine. During the presentation, I will describe the status of scientific activity based on THz radiation and currently used laboratory equipment. A particular attention will be paid to a 30-years old technique, the THz time domain spectroscopy, which is the source of unquestionable rapid development of THz-related activities. I will also describe a few examples of a basic research in which THz techniques were used in quantum optics, semiconductor physics and medicine.