Tiles can be made of ceramics, mosaics, and natural stone. Likewise, the environment in which they are used is equally diverse: walls, floors, and staircases in houses, offices, gardens, factories, public buildings, and places of worship. This means that tilers may be expected to work both inside and outside, accurately following designs, preparing surfaces, laying tiles to the correct pattern, and grouting to a high standard. Tilers sometimes specialize in certain areas of artistic work; for example, the complex designs seen in swimming pools.