Tatami mats are a traditional type of Japanese flooring. Traditionally made of rice straw to form the core (though nowadays sometimes the core is composed of compressed wood chip boards or polystyrene foam), with a covering of woven soft rush (igusa) straw, tatami are made in uniform sizes.
Usually, on the long sides, they have edging (heri) of brocade or plain cloth, although some tatami have no edging.
Tatami were originally a luxury item for the nobility. During the Heian period, when the shinden-zukuri architectural style of aristocratic residences was consummated, the flooring of shinden-zukuri palatial rooms were mainly wooden, and tatami were only used as seating for the highest aristocrats. In the Kamakura period, there arose the shoin-zukuri architectural style of residence for the samurai and priests who had gained power. This architectural style reached its peak of development in the Muromachi period, when tatami gradually came to be spread over whole rooms, beginning with small rooms. Rooms completely spread with tatami came to be known as zashiki (lit., room spread out for sitting), and rules concerning seating and etiquette determined the arrangement of the tatami in the rooms.It is said that prior to the mid-16th century, the ruling nobility and samurai slept on tatami or woven mats called goza, while commoners used straw mats or loose straw for bedding.
The lower classes had mat-covered dirt floors.
Tatami were gradually popularized and finally reached the homes of commoners toward the end of the 17th century.
Houses built in Japan today often have very few tatami-floored rooms, if any. Having just one is not uncommon. The rooms having tatami flooring and other such traditional architectural features are referred to as nihonma or washitsu, "Japanese-style rooms".
Tatami mats in Japanese culture are flooring surfaces to be kept as clean as a bed surface or dining table surface. Nowadays, they are commonly associated with Japanese religious rites and the tea ceremony. Most modern Japanese homes still have at least one tatami room, the washitsu which is furnished and decorated in the traditional Japanese style.
Tatami are also used when training in Japanese martial arts, such as judo, for protective purposes.
Tatami "omote", or the outside rush mat layer, wrapped over the rice straw core of the mat, is used in the practice of tameshigiri in Japanese swordsmanship. The tatami omote mats are rolled into cylinders, soaked in water for several days, and then cut in order to test either a newly made sword's sharpness or a swordsman's skill.