The field of smart materials and structures is emerging rapidly with technological innovations appearing in engineering materials, sensors, actuators and image processing. Smart materials can be defined in several ways : 1. Materials functioning as both sensing and actuating 2. Materials, which have multiple responses to one stimulus in a coordinated fashion 3. Passively smart materials with self-repairing or stand-by characteristics to withstand sudden changes 4. Actively smart materials utilising feedback 5. Smart materials and systems reproducing biological functions in load bearing systems. Smart materials can be either inorganic, organic or composites. In this article, different groups of smart materials are presented and their properties are discussed.