This document provides an overview of biosensors and nanobiosensors. It discusses that a biosensor combines a biological component with a physicochemical detector. It then describes the basic components and working principle of biosensors, including the biological recognition element, transducer, and detector. Some examples mentioned include glucose monitoring devices and pregnancy tests. The document also discusses nanobiosensors and how nanoparticles can enhance sensitivity and specificity. Applications mentioned include food analysis, medical diagnosis, and environmental monitoring. In the future, nanobiosensors may allow for applications like electronic paper, morphing devices, and smart contact lenses.