During ancient times, humans did not live in houses. Instead, they lived in caves. Then, humans learned to use animal skins, sticks, leaves and soil to build simple huts and tents. Gradually, humans stared to use stronger materials such as wood, rocks, cement, concrete and iron to build houses.
In olden days, humans used tree trunks to build bridges. Then, wood and planks were used to build stronger bridges. In 1779, Abraham Darby built the first iron bridges. Nowadays, bridges are mostly built from concrete that is supported by strong steel structures.