Pearlitic steel, or pearlite, is one of the strongest materials in the world, and can be made into long, thin wires. The strength of pearlite allows it to support very heavy weight, and it has the unique ability to stretch and contract without breaking (ductility). Ductility is important for building bridges, because even very strong materials can break when subjected to stretching if they are not ductile enough. This is why structures made of concrete can still collapse during violent earthquakes. Pearlite is used for suspension bridges to help them withstand strong shaking while supporting heavy weight.