Strain sensors have become fundamental to contemporary sensing technology, driven by the growing demand for flexible, sensitive, and durable transducers across medical care, robotics, structural monitoring, and human-machine interfaces. Rapid advances in strain sensing performance---in terms of gauge factor, detection limit, working range, and operational stability---have enabled next-generation wearable and implantable sensing systems. This mini review examines sensing mechanism classifications, key performance parameters, sensor architectures, and application domains, with a unified focus on how sensing capability can be maximised for real-world deployment. Particular emphasis is placed on... More >