This paper addresses some of the fundamental issues and critical advantages in reducing the grain size/ feature size to the nanoscale regime. We find that as the grain size or feature size is reduced, there is a critical size below which the defect content can be reduced virtually to zero. This critical size for most defects in solid state materials falls in the nanoscale regime. Thus, nanostructured materials offer a unique opportunity to realize the property of a perfect material. However,

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... h this opportunity comes a great challenge in terms of engineering a large fraction of atoms near the surfaces/interfaces. Since the fraction of atoms near the surfaces/interfaces increases inversely with size, this fraction can get closer to unity and determine efficacy of nanostructured materials in terms of efficiency, stability and reliability of nanostructures. We discuss briefly ways to enhance the stability and reliability of nanostructured systems by controlling the properties of interfaces.