Fuel cells are expected to soon become a source of low- to zero-emission power generation for applications in portable technologies and electric vehicles. Allowing development of high quality solid electrolytes and production of smaller fuel cells, significant progress has been made in the development of fuel cell membranes using nanotechnology. Nanostructures have been recognized as critical elements to improve the performance of fuel cell membranes. This paper provides an overview of research and development of nanostructured membranes for different fuel cell applications and focuses on improvement of fuel cell membranes by these nanostructures. Theoretical studies using molecular-scale modeling and simulation of fuel cell membranes have also been included in this review. Other issues regarding the technology limitations, research challenges and future trends are also reviewed. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.