Starting from the very definition of smart structures and smart materials, this paper addresses the fundamental mechanism of operation of some well known smart materials like piezoelectric ceramic/polymer, electrostrictive ceramic, magnetostrictive alloy, shape memory alloy, electroheological fluid, magnetoheological fluid, optical fibers and so on. It also describes briefly the working principles of the actuators and sensor based upon these materials. In addition to that an overview of the various applications and research dealing with the application of these smart materials in aerospace structures mainly in the context of vibration suppression, shape control and adaptive structures for their efficient functioning has been presented. On the whole the presentation stresses on actuators. Since it is the actuator not the sensor that is often the limiting factor in smart structure used for active control. Numerous investigations have been made and are on the way to improve upon the piezoelectric and electrostrictive actuator for greater generating force and larger stroke, as well as shape memory alloy actuator for fast response. Development of multilayer piezoelectric and electrostrictive actuator and discovery of precompressed piezoelectric element and actuator is a forward leap in that direction.