Nikolaus Otto is credited with inventing the first functional four-stroke internal combustion engine, which burned fuel directly inside a cylinder to move a piston. Unlike the massive external combustion steam engines of the time, Otto’s engine was compact, powerful, and relatively efficient. This invention provided the necessary power-to-weight ratio to make automobiles, motorcycles, and eventually airplanes possible. The four-stroke cycle (intake, compression, power, and exhaust) is still known as the 'Otto Cycle' and remains the standard for the vast majority of cars on the road today. It fundamentally shifted the world’s energy dependence toward petroleum and sparked the rapid urbanization and suburbanization of the 20th century, changing the physical landscape of the planet through the creation of road networks.