Micro-Electro-Mechanical Systems (MEMS) are devices that are fabricated using techniques similar to those used for integrated circuits (ICs) to create micrometer-sized mechanical structures (suspended bridges, cantilevers, membranes, fluid channels, etc.) that are often integrated with analog and digital circuitry. MEMS can act as sensors, receiving information from their environment, or as actuators, responding to a decision from the control system to change the environment. The ITRS has organized a MEMS Technology Working Group (TWG) which has developed a new chapter on MEMS for its 2011 report. The report focuses on MEMS technologies associated with mobile internet devices, such as smart phone and tablet computers. These applications represent the fastest growing segment in MEMS manufacturing, according to 2011 market forecasts by iSuppli, Yole Development, and SEMI. The report focuses on the leading MEMS devices used in mobile internet applications: accelerometers and gyroscopes, microphones, and RF MEMS, including resonators, varactors, and switches. The report also reviews emerging MEMS applications, including optical filters, picoprojectors, the electronic nose, microspeakers, and ultrasound devices.