Biosensors are devices that analyze biological samples to understand structure and function and for diagnostics. They have various uses including molecule analysis, food safety testing, medical monitoring, and detection of biological weapons. A biosensor consists of two main components: a bioreceptor that recognizes the target analyte, and a transducer that converts the recognition event into a measurable signal. Common types of biosensors include calorimetric, potentiometric, amperometric, and optical biosensors. Examples of biosensors include blood glucose monitors used by diabetics, heart and blood pressure monitors, and pregnancy tests. Wearable biosensors are also being developed for applications like smart contact lenses, sweat analysis, and glucose monitoring.