A doll is a model of a human being, often used as a toy for children. Dolls have traditionally been used in magic and religious rituals throughout the world, and traditional dolls made of materials such as clay and wood are found in the Americas, Asia, Africa and Europe. The earliest documented dolls go back to the ancient civilizations of Egypt, Greece and Rome. The use of dolls as toys was documented in Greece around 100 AD. They have been made as crude, rudimentary playthings as well as elaborate art. Modern doll manufacturing has its roots in Germany, going back to the 15th century. With industrialization and new materials such as porcelain and plastic, dolls were increasingly mass-produced. During the 20th century dolls became increasingly popular as collectibles.