Archaeologists and researchers use the broken pieces of pottery or ceramics ("sherds") that they find during their search for and excavation of ancient settlements to learn many things about the people who once lived there. These pieces of pottery can provide clues about the age of the settlement that lies buried below the surface and the types of activities that took place there. Just by looking at the sherd, archaeologists can often recognize the size, shape, and date of the vessel based on the sherd's shape, the material used to temper the vessel, and the designs incised into or painted onto its surface. The date of the vessel will also apply to the settlement underneath the surface. Ancient societies changed the shape of their pottery vessels and their designs over time, sometimes quite rapidly, and archaeologists have been able to develop "ceramic chronologies" for different regions of the world. They do this by excavating and dating (using carbon-14 or other methods) ancient settlements of different ages and determining what the pottery of different time periods looked like.