Brick is a building material obtained by mixing clay, earth, or similar materials with water, shaping them, drying them, and usually firing them in a kiln. Today, it is used in reinforced concrete structures for many purposes, such as infill, walls, and cladding, in addition to the load-bearing system. The first bricks were unfired adobe (sun-dried clay blocks), but later they began to fire bricks in kilns to make them more durable. This made the material more resistant to water and time. Industrial bricks fired at high temperatures are widely used in interior and exterior walls, chimneys and furnaces, and aesthetic cladding.