This review article describes recent developments in microfluidics, with special emphasis on disposable plastic devices. Included is an overview of the common methods used in the fabrication of polymer microfluidic systems, including replica and injection molding, embossing, and laser ablation. Also described are the different methods by which on-chip operations--such as the pumping and valving of fluid flow, the mixing of different reagents, and the separation and detection of different chemical species--have been implemented in a microfluidic format. Finally, a few select biotechnological applications of microfluidics are presented to illustrate both the utility of this technology and its potential for development in the future.