Mechanical Engineering addresses the analysis and development of technological systems involving motions, and allows people to harness the energy and forces that exist in nature to provide for the needs of society. Mechanical engineers are responsible for the conception, design, manufacture, control, maintenance and management of such systems. Mechanical systems may comprise mechanisms or machines made up of moving components or involve fluid flow within or around solid structures to impart forces or energy interactions. These could range from micro-mechanical devices through to massive power generating turbines. Modern air and ground transport systems, and thermal power generation are key examples of Mechanical Engineering accomplishments.