The document discusses smart materials and their applications in engineering. It defines smart materials as materials that can change their mechanical properties in response to external stimuli like magnetic fields, temperature, or electric currents. Some examples of smart materials mentioned are magnetorheological fluids, shape memory alloys, and piezoelectric materials. The document then provides more details on how these different smart materials work and examples of their applications, such as using shape memory alloys in medical implants or generating electricity with piezoelectric materials.