The microfluidic devices have recently attracted tremendous interest due to their potential of bringing novel applications into reality in many areas including biomedical industry. However, the challenges in the design of microfluidic devices still remain since all aspects of fluid flow in microchannels have not been yet fully understood. This paper presents major findings in the literature on fundamentals of flow physics in microchannels. The review is intended to provide an extensive overview on the available knowledge base as well as the areas that require intensive investigation. It includes studies on both pressure-driven and electro-osmotic flows in microchannels. (c) 2005 Elsevier Ltd. All rights reserved.