A piston is a key component in a reciprocating engine, which is found in most cars. It is a cylindrical piece of metal with piston rings that help to form an air-tight seal once the piston is installed within the engine cylinder. The piston is attached via a piston pin or gudgeon to a connecting rod, which in turn is connected to the crankshaft. In four-stroke (petrol and diesel) car engines, the intake, compression, combustion, and exhaust process takes place above the piston in the cylinder head, which forces the piston to move up and down within the cylinder, which causes the crankshaft to turn. The pistons function is to act as a movable plug in the cylinder, forming the bottom part of the combustion chamber. The power in an engine all comes from the force pushing on the top of the piston, which is determined as the area of the piston multiplied by the gas pressure. The piston is still seeing ongoing development and research as it is a major area of focus for improving the efficiency of engines.