The late 1980s to the end of the 1990s saw label-free, real-time biosensing move from concept to practice, driven by plasmonic, optical, and electrochemical readouts. Researchers integrated transducers, biorecognition interfaces, and signal processing to enable rapid biomolecular detection and device-oriented research across disciplines. Historical Significance: This period established the foundational architectures and concepts that underpin modern diagnostics, including real-time monitoring, non-invasive surface interrogation, and robust enzyme-based sensing, setting the stage for pervasive diagnostic devices and cross-disciplinary collaboration.