Mechanical Engineering is the application of physical principles and mathematics to the creation of useful devices, objects and machines. Mechanical engineers use principles such as heat, force, and the conservation of mass and energy to analyze static and dynamic physical systems, in contributing to the design of things, such as: automobiles, aircraft, and other vehicles, heating and cooling systems, household appliances, industrial equipment and machinery, weapons systems, etc. In brief, Mechanical Engineers are problem solver for the society. They research, develop, design, manufacture, and test tools, engines, machines, and other mechanical systems. They also work on power-producing machines. They develop machine tools, industrial production equipment, and robots. Mechanical engineers also design tools that other engineers need for their work. The emerging fields of Micro-Electro-Mechanical Systems and Nanotechnology, which involves the creation of high-performance materials and components by integrating atoms and molecules, is introducing entirely new principles to the design process. Social needs and new technologies and skills change the profession as it seeks to fit a wide-open global marketplace.