<p>Over the past decades, terahertz technology has emerged as a novel biologic analytical tool. Terahertz waves are not radio waves or visible lights, but possess unique optical characteristics, which have a wide range of applications in molecular fingerprinting, structural bio-molecular analysis, and microenvironmental analysis at cellular and tissue levels. Because of its ability to probe fundamental interactions, terahertz technology allows for a deeper understanding of intricate biological systems through non-destructive detection methods. Despite significant advances, some challenges, such as limited spectral selectivity and significant absorption in aqueous environments, remain unaddressed. In this review, we aimed to highlight recent developments in terahertz spectroscopy, focusing on theoretical principles, applications in bio-sensing, and methodologies to overcome the limitations of biological applications.</p>