Biochips, in all of their guises are the most active area of research and development in the analytical sciences. These micro-miniature devices are produced using techniques originally developed in the microelectronics and in the printing industry. Although some microchip devices have been commercialized (e.g., capillary electrophoresis chips), many challenges and issues remain for the routine implementation of these micro-analytical devices. These include surface chemistry effects in the sub-microliter confines of a microchip chamber, the interface between the <1 cm2 microchip and the human operator, utilization of plastics for construction, and the development of low cost, mass production methods. Biochips design has usually been empirical, but new micro-fluidics modeling software offers a route to rational design of at least the fluidic components of biochips. The current scope of applications for biochips include protein and nucleic acid analysis, genetic tests, cell selection, immunoassay, and various molecular separation techniques. A goal in biochip research is integration of all steps in an analytical process on a single chip - the so-called "lab-on-a-chip", and there are a range of biochips that combine several sequential steps of an overall analytical procedure on a single disposable biochip device. The benefit of this approach is faster and simpler analysis. Further miniaturization of the biochip will lead to the nanochip, i.e., a device with dimensions less than 100 nanometers. Nanotechnology is at an early stage, but already significant progress has been achieved in directions that may lead to useful analytical devices (e.g., carbon nanotubes). The control of atomic and molecular composition of surfaces in a nanochip device may provide unexpected improvements in analytical performance over conventional devices in which surface composition is imperfectly controlled, and much remains to be done in this active and speculative area of research.