MicroElectronic Mechanical Systems (MEMS) have revolutionized the market for sensors by providing small, fast-responding measurement devices at very low cost. These measurement devices have been widely accepted in many areas of engineering and have vastly contributed to safety, reliability, and efficiency of many products. As of the present, however, the benefits offered by MEMS have not yet been exploited in HVAC&R systems. This is bound to change. The availability of MEMS sensors will enable the development of comprehensive fault detection and diagnostics (FDD) for improved system efficiency and reliability. The combination of MEMS sensors, FDD, and networking capabilities will change how refrigeration and air-condition systems are monitored and serviced. This paper gives an overview of MEMS and FDD methods, and provides examples of application opportunities for MEMS in vapor compression systems.