Find the best mechanical engineering lessons, classes, and instructors at HeyKiki and learn all about mechanical engineering. Mechanical engineering combines theories and approaches from engineering, materials science, and physics to design, produce, and maintain mechanical tools, machines, or systems. It wasn't until the 18th century that mechanical engineering existed as a profession you could study and practice. Today, they mechanical engineers are responsible for building manufacturing plants, robotics, airplanes, boats, medical and transportation systems, weapons, heating and cooling systems, and much more. It is a field of constant innovation!