Terahertz (THz) radiation occupies the electromagnetic (EM) spectrum region between approximately 30 μm and 1 mm (10 THz-300 GHz). Recent advances in methods of producing THz radiation have stimulated interest in studying mechanism and application of THz radiation. Applications of THz radiation in biomolecular sensing and spectroscopy are very important due to the benefits of THz-TDS. This paper briefly summarizes various methods used to generate and detect THz radiation and reviews particularly current understanding of the interactions between THz radiation and biomolecules (protein and DNA).