"The ancient Greeks believed that eyes are the source of beams of light that allow human beings to see. In Greek mythology THEIA, Titan goddess of sight, was in fact the mother of the Sun, Moon, and Dawn. Gaining from this inspiration, this research plan focuses on the development of accessible technologies to exploit the several probing capabilities demonstrated by Terahertz (THz) waves, targeting applications in fields like medicine, biology, material science. Over the last few years, Terahertz Time-Domain Spectroscopy (THz-TDS) has become a highly promising tool for real-time spectroscopy analysis of a wide variety of materials. Although TDS based on the transmission of THz waves through materials reached a form of standardization due to its simplicity of operation, there is a common consensus that spectroscopy in reflection mode would be required for most THz-TDS. THEIA explores the capability of the reflective-THz spectroscopy proposing key-enabling solutions (e.g. the use of waveguide technologies) to the several technological and practical constrains that currently limits its application deployment. THEIA will investigate the waveguide delivery of ultra-wide band THz pulse toward a sample and the recollection and detection through same structure. In addition in such a framework, it will present a structured approach to solve the inherent problem in real world scenarios of the lack of reference signals –required for THz-TDS- in compound detection via reflective spectroscopy. Taking also into account disabling issues like the unknown position of the target and the significant contribution of the sample surface roughness, THEIA will establish a consistent technique of inference respect to databanks of known fingerprints to recognize complex compounds, paving the way to a new form of remote electromagnetic probing device."