Many of us own portable computers, telephones and audio/video equipment that did not exist a decade ago. The reason for this rapid change is that miniaturizing and integrating of electronic and electromechanical components are still an ongoing processes. The general strategy to miniaturize and integrate can also be applied to other scientific fields such as chemistry and the life sciences. There is a vision that all stages of chemical analysis, such as preparing and purifying a sample, handling of liquids, detecting and analyzing a signal, will one day be integrated and automated on a single microsystem. The idea behind this vision is, that such a system is portable and delivers more and qualitative better data more rapidly than a conventional system, while using only very small amounts of the reagents. To realize such a system, components from different fields, such as electronics, optics, mechanics and fluidics, have to be miniaturized. In this book we will discuss the different aspects of (bio)chemical microsystem development, which are simulation, design, materials, microfabrication, microliquid handling components, interconnections, integration and applications. These topics are illustrated with examples, mainly from research projects at Mikroelektronik Centret.