Unknown We can expect many new fields of engineering to emerge as technology advances in the 21st century. Some of these fields are apparent today. Fields such as micro-electro-mechanical systems (MEMS), mechatronics (robotics), nanotechnology, synthetic biology, and smart technologies (cars, structures, buildings, etc.) are all emerging engineering fields. New engineering fields are often multidisciplinary and hold enormous opportunities for future engineers. The following chapters are devoted to three specific emerging engineering fields. Bioengineering combines the analytical and experimental methods of engineering with biology and medicine to produce a better understanding of biological phenomena and develop new therapeutic techniques and devices. Students with bioengineering degrees may work as biomedical engineers to develop new medical techniques, medical devices, and instrumentation for hospitals or individual patients. Electrochemical engineering is a combination of electrical engineering and chemical engineering. While the subject involves some mature technologies, such as the synthesis of chemicals, refining metals, the development of new batteries and fuel cells, electroplating, etching, and corrosion resistance, it also holds a central position in the development of new generations of hybrid cars as well as being important in the development of the core technology for all-electric vehicles of the future. Green energy is energy produced from sources that are environmentally more friendly (or “greener”) than fossil fuels (coal, oil, and natural gas). Green energy includes all renewable energy sources (including solar, wind, geothermal, biofuels, and hydropower), and by definition, should also include nuclear energy (though there are many environmentalists who oppose the idea of nuclear energy as green energy because of the nuclear waste issues, accidents, and its harmful environmental effects).