Piezoelectric materials are special substances that generate an electric charge when they are mechanically stressed. This means that when these materials are squeezed, twisted, or otherwise deformed, they produce electricity. Common examples of piezoelectric materials include certain ceramics, crystals, and polymers, which are used in various applications like sensors, actuators, and microphones. These materials work in the opposite way as well; when an electric field is applied to them, they change shape. This property makes piezoelectric materials useful in devices such as ultrasonic transducers and vibrating motors, where precise movements are required in response to electrical signals.