Quern-stones have been used by numerous civilizations throughout the world to grind materials, the most important of which was usually grain to make flour for bread-making. They were generally replaced by millstones once mechanised forms of milling appeared, particularly the water mill and the windmill, although animals were also used to operate the millstones. However, in many non-Westernised, non-mechanised cultures they are still manufactured and used regularly and have only been replaced in many parts of the world in the last century or so.