In recent years, various fuel cell models based on computational fluid dynamics (CFD) have been developed at the Fuel Cell Laboratory, University of Miami. These 2-or 3-dimensional models account for all the major transport phenomenon in all the major components of a fuel cell: two flow fields, two gas diffusion layers, two catalyst layers and the membrane. If necessary, collector plates, cooling channels and other components can easily be included in the modeling domain. These models can provide detailed multi-dimensional distributions of species concentrations, current density, over-potential, temperature, water content and reaction rates, as well as polarization curves. Application of these CFD-based models to various fuel cell operation situations will be presented and the uniqueness of such multi-dimensional models will be discussed. The limitations of such models and the need for multidisciplinary research, including those micro/nanoscales, will be addressed.