Smart polymers are materials that change properties in response to environmental stimuli like temperature, pH levels, or magnetic fields. Some examples include piezoelectric materials that produce electricity with stress or change shape with electric current, thermoresponsive polymers that alter shape based on temperature, and shape memory alloys that change shape with magnetic fields and return to original shape with heat. These smart polymers have applications as biomaterials in drug delivery, cancer therapy, medical devices, and more.