An is a belt of varying size and shape worn with both traditional Japanese clothing and uniforms for Japanese martial arts styles. Originating as a simple thin belt in Heian period Japan, the developed over time into a belt with a number of different varieties, with a number of different sizes and proportions, lengths, and methods of tying. The , which once did not differ significantly in appearance between men and women, also developed into a greater variety of styles for women than for men. Despite the kimono having been at one point and continuing to appear to be held shut by the , many modern are too wide and stiff to function in this way, with a series of ties known as , worn underneath the , used to keep the kimono closed instead. are categorised by their design, formality, material, and use, and can be made of a number of types of fabric, with heavy brocade weaves worn for formal occasions, and some lightweight silk worn for informal occasions. are also made from materials other than silk, such as cotton, hemp and polyester, though silk are considered a necessity for formal occasions. In the modern day, pre-tied , known as or , are also worn, and do not appear any different to a regular when worn. Though can be inexpensive when bought second-hand, they typically cost more than a kimono, particularly when purchased brand-new. A number of specialist fabrics used particularly to make are highly prized for their craftsmanship and reputation of quality, such as , produced in the Nishijin district of Kyoto, and produced in Fukuoka prefecture. History Heian period to Edo period In its early days, the was a cord or ribbon-like sash, approximately in width. Men's and women's were similar. At the beginning of the 17th century, both women and men wore a thin, ribbon-like . By the 1680s, the width of women's had already doubled from its original size. In the 1730s women's were about wide, and at the turn of the 19th century were as wide as . At that time, separate ties and cords were necessary to hold the in place. Men's were widest in the 1730s, at about . Before the Edo period, which began in the mid-1600s, robes were fastened with a narrow sash at the hips. The mode of attaching the sleeve widely to the torso part of the