A structure is an assembly that serves an engineering function. It is reasonable to expect that all engineering design should be smart, and not dumb. But one can still make a distinction between smartly designed structures and smart structures. The latter term has acquired a specific technical meaning over the last few decades. A smart structure is that which has the ability to respond adaptively in a pre-designed useful and efficient manner to changes in environmental conditions, including any changes in its own condition; the response is adaptive in the sense that two or more stimuli or inputs may be received as anticipated and yet there is a single response function as per design. Smartness ensures that the structure gives optimum performance under a variety of environmental conditions. While structures with some degree of smartness have been designed from times immemorial, the current activity and excitement in this field derives its impetus from the level of sophistication achieved in materials science, information technology, measurement science, sensors, actuators, signal processing, nanotechnology, cybernetics, artificial intelligence, and biomimetics.