A doll is a model typically of a human or humanoid character, often used as a toy for children. Dolls have also been used in traditional religious rituals throughout the world. 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. They have been made as crude, rudimentary playthings as well as elaborate art. Modern doll manufacturing has its roots in Germany, from 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.