In this presentation, my journey of studying an “unexplored” region of electromagnetic radiation, so-called terahertz(THz) wave using convection electrons will be reviewed. This electromagnetic spectrum is veiled until last several decades and is still called as “THz gap” due to the lack in practical sources both electronically and optically. However, an attention in THz wave and its interaction with various matters, especially soft matter such as biomedical systems, has been growing exponentially ever than before. The biomedical systems such as biomolecules, tissues and organs are biologically active only in water. Many are now realizing we have ignored the water in biomedicals as a passive solvent. The water dances together with biomolecules in ~picosecond time scale at room temperature. I will introduce how potentially THz wave might take a role in understanding the energy transfer mechanism and pathway in biomedical systems via water. I acknowledge NRF and SNU supported an extra four years after my retirement to continue this work.