Since its expanded use in Ancient Rome, concrete has been a material that has had many varied uses. However, the nature of concrete is that is has little tensile strength. This means that its applications are limited to those situation where only compressive strength is important - that is, until the development of reinforced concrete. There are many ways to do this, but most examples create reinforcement from inside the concrete by using either iron or steel to make it have more tensile strength. This not only provides a way for greater spans to be developed, but also very unique shapes, as the reinforcement can take on all kinds of shapes, over which the concrete is poured. Modern roads are made with this technique as well.