Microfluidics is the science and technology of manipulating miniscule volumes of fluids. It is a burgeoning field of research and development with applications to drug discovery, nano-synthesis, biomedicine, and cell biology. Micromachining of silicon combined with hermetic glass bonding enables the precise, batch fabrication of robust 3D microstructures that, while often resembling macroscopic devices which inspired their design, exhibit capabilities which are enhanced or uniquely enabled by microscopic dimensions. Several examples will be presented, followed by a discussion of cost/performance challenges and competing manufacturing methods and materials.